Institute of Solid State Physics Institut für Festkörperphysik 2007-2008

Transcription

Technische Universität Berlin
Institute of Solid State Physics
Institut für Festkörperphysik
2007-2008
Technische Universität Berlin
Institute of Solid State Physics
Institut für Festkörperphysik
2007 – 2008
Hardenbergstr. 36
D-10623 Berlin
Germany
Phone:
Fax:
E-Mail:
(30) 314-220 01
(30) 314-220 64
ifkp@physik.tu-berlin.de
Front Cover
The front cover shows steps important for the development of single photon (q-bit) emitters.
Top left: SEM image of etched mesa structures. Bottom left: SEM image of the completely
processed device. Top right: Measured photon correlation function, demonstrating true single
photon emission. Bottom right: 3D simulation of the device. Center: Photo of an array of ten
single photon emitters ready for measurement.
Design of cover: Dipl.-Phys. Erik Stock und Dipl.-Phys. Anatol Lochmann, AG Bimberg
Back Cover
Some of the larger projects and agencies funding our work, 2007 - 2008.
Layout: Dipl.-Phys. K. Pötschke, AG Bimberg
Explanation of the Acronyms on the Back Cover:
NATAL: „Nano-Photonics Materials and Technologies for Multicolor High-Power Sources“
is an EU FP 6 STREP
TRIUMPH: „Transparent Ring Interconnection Using Multiwavelength Photonic Switches“
is an EU FP6 STREP
RAINBOW: "High quality material and intrinsic properties of InN and indium rich nitride
Alloys"
is an EU Marie Curie Initial Training Network (ITN)
VISIT: “Vertically Integrated Systems for Information Transfer”
is an EU FP7 STREP
SFB 787: “Semiconductor NanoPhotonics”
is the Collaborative Research Center 787 of German Science Foundation – DFG
AGeNT: “Arbeitsgemeinschaft der Nanotechnologie-Kompetenzzentren Deutschlands”
The “Association of the Nanotechnology Centers of Competence in Germany”
is funded by the BMBF
100 x 100 Optics: “100 Mbit/sec for 100 Million Users”
is a project of the “Fund for Future Development of the State of Berlin”
MuLF : “Multimedia Center for Teaching and Research”
is funded by BMBF.
PolarCon: “Polarization Field Control in Nitride Light Emitters"
is a German Science Foundation - DFG - Transregional Research Group
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CONTENTS
1.
PREFACE
5
2.
PRIZES AND AWARDS
9
3.
STRUCTURE AND STAFF OF THE INSTITUTE
3.1
3.2
3.3
3.4
3.5
3.6
3.7
4.
Office of the executive director (01.01.2008)
Departments of the institute
Workshops
Center of NanoPhotonics
Affiliated scientific units
External and retired faculty members of the institute
Honorary, adjunct and guest professors, Humboldt awardees and fellows
FOREIGN GUESTS
4.1
5.
Talks by Guests
PARTICIPATION IN COMMITEES
5.1
5.2
Program and Advisory Committee
Editorial duties / Boards of institutes and companies
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15
19
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25
29
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6.
EXTERNAL COLLABORATIONS
35
7.
TEACHING
39
8.
PATENTS
43
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9.
SCIENTIFIC ACTIVITIES
9.1
Department I
9.1.0
Staff
9.1.1
Summary of activities
9.1.2
Books
9.1.3
Publications
9.1.4
Invited talks
9.1.5
PhD theses
9.1.6
Diploma theses
9.1.7
Abstracts of selected papers of department I
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47
51
51
63
67
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69
9.2.
Department II
9.2.a Department IIa
9.2a.0
Staff
9.2a.1
9.2a.2
Publications
9.2a.3
Invited talks
9.2a.4
PhD theses
9.2a.5
Diploma theses
9.2a.6
Abstracts of selected papers of department IIa
9.2.b Department IIb
9.2b.0
Staff
9.2b.1
9.2b.2
Publications
9.2b.3 Invited talks
9.2b.4 PhD theses
9.2b.5
Diploma theses
9.2b.6
Abstracts of selected papers of department IIb
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89
91
97
99
99
101
111
111
113
115
121
123
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9.3
Department III
9.3.0
Staff
9.3.1
9.3.2
Publications
9.3.3
Invited talks
9.3.4
PhD theses
9.3.5
Diploma theses
9.3.6
Abstracts of selected papers of department III
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135
137
139
141
143
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145
9.4
Department IV
9.4.0
Staff
9.4.1
9.4.2
Publications
9.4.3
Invited talks
9.4.4
PhD theses
9.4.5
Diploma theses
9.4.6
Abstracts of selected papers of department IV
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149
151
153
157
159
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163
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1.
PREFACE
The Institute of Solid State Physics presents its tenth biannual progress report. Founded in
1974 the Institute is located since 1985 at its site in Hardenbergstraße next to the center of
Berlin, where it disposes of spacious lecture halls, seminar rooms and state-of-the-art
laboratories. Our scientific work is focussed on epitaxial growth of narrow and wide-gap
semiconductor hetero- and nanostructures, physics of nanostructures, novel materials research
as well as physics and technology of nano-photonic devices and systems. In addition,
development of nanoscopic measurement techniques, like cathodoluminescence, cross-section
scanning tunneling microscopy, near field scanning optical microscopy, microphotoluminescence, and micro-Raman are common subjects of the research activities of our four
scientific departments.
In the “Center of NanoPhotonics” CNP of the institute novel devices like Single Photon
Emitters, Quantum Dot Vertical Surface Emitting Lasers, QD High Speed Emitters,
QD Semiconductor Optical Amplifiers, QD VECSELs, Nanoflash memories, ultraviolet
LEDs, and high brilliance green laser diodes… are developed based on materials like
InGaAsSb/GaAs or InAlGaN. Most modern education and research on devices and their
technology are offered here to our students and PhD candidates. In addition, the CNP
provides assistance to small and medium size companies and acts as incubator for three startups: VI Systems in Berlin, PBC Lasers in Berlin and Azzurro Semiconductors in Magdeburg.
Our epitaxial growth facilities were decisively extended by the installation of a new CloseCoupled-Showerhead Thomas Swan GaN MOCVD system purchased from Aixtron, which is
now fully operationell.
An additional faculty member was appointed in 2008: Prof. Janina Maultzsch, formerly at
Columbia University in New York, returned to the institute and is working closely with the
research group of Christian Thomsen. A new chair in “Optoelectronics” was created and the
appointment procedures were initiated.
The success of the institute and its large number of students, PhD candidates and postdocs it
employs depends now since more than a decade mostly on external financial resources. The
funding from TUB and our state government in Berlin covers less than 20 % of cost of
consumables and equipment. Our most important funding agency continued to be the German
Research Foundation (DFG). Our proposal for a new Collaborative Research Center
“Semiconductor Nanophotonics” (Sfb 787), initiated by Prof. Dieter Bimberg and headed
now by Prof. Michael Kneissl found the acceptance both of the reviewers, and the deciding
bodies of DFG. The Collaborative Research Center is funded since January 1st, 2008 for four
years with two possible prolongations until end of 2019. Cooperation on nanostructure and
photonic device research with colleagues from five other institutions in Berlin (Humboldt
University, Ferdinand-Braun-Institute, Heinrich-Hertz-Institute, Weierstraß-Institute, KonradZuse-Center) presents the basics of the Sfb 787. In addition, smaller projects focussing on
Nanomemories, on GaN-based Semiconductor Disk Lasers as well as silicide nanowires were
funded by DFG.
Complementary important funding comes from the government of the State of Berlin in the
frame work of its “Zukunftsfonds” and ProFIT Programs, the European Union within its FP 6
and 7 Programs and the NATO Program Science for Peace.
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The BMBF national competence center CC NanOp (Nano-Optoelectronics), established in
October 1998, presented again a very effective and successful means for initiating important
European programs on nano devices like NATAL, TRIUMPH, RAINBOW, and VISIT.
Many of these projects emerged from small scale projects, so called “Machbarkeitsstudien”,
financed via NanOp. TUB therefore decided to continue its support of CC NanOp until end of
2010. Based on this decision the Federal Ministry of Education and Research (BMBF)
decided to entrust TUB with the coordination of all National Centers of Competence in
Nanotechnology within a new body called AGeNT, funded until beginning of 2011.
We are particularly proud of being initiator and member of the European Union Center of
Excellence SANDiE in the field of semiconductor nanostructures which continues its
operation for four more years until 2012. Strong links to leading international optoelectronic
and communication companies like Aixtron, Bookham, INTEL, OSRAM Opto
Semiconductors, Sentech and Jenoptik have been established within the framework of the
above mentioned and bilateral programs.
In order to protect our intellectual property better than in the past and to have a better basis for
cooperation with the industry, we filed and obtained an appreciable number of patents. The
support by our local patent agency IPAL proved to be of outmost importance.
We are very grateful to all our funding agencies, their administrators and cooperating industry
for their continuous help and encouragement.
The scientific part of the present report will certainly provide sufficient evidence that the
funding we received carried excellent results. Particular appreciation of our scientific
achievements was expressed by the bestowal of a number of awards listed in part 2 of the
report and particularly.
We are particularly proud on the bestowal of an Alexander von Humboldt Award in 2008 to
Professor Shin-Lien Chuang from University of Illinois at Urbana- Champaign, who joined us
since the beginning of 2009, focussing his activities on nanophotonic devices. Professor Gadi
Eisenstein, Technion Haifa, Humboldt Awardee 2006 continues to be in Berlin on a regular
basis. Dr. Jungho Kim from South Korea received not only a Marie Curie Stipend, but was
receiving in summer 2008 an appointment to a professorship in Soeul.
Scientific contacts with institutions at many different locations in Europe, Japan or USA
continued to flourish. Especially strong collaborations and links developed or continued to
exist to research institutions and universities in St. Petersburg, Novosibirsk, Cambridge,
Göteborg, Cork, South Carolina … to mention only a few.
Physics is a science not bound to a country or to borders. This ”discovery” led to an
increasing number of our students and scientists in the past to pursue their research at foreign
universities in Tokyo, St. Petersburg, Glasgow, Texas, Berkeley, … to mention only a few.
We would like to thank particularly their local hosts. We will further encourage our coworkers to combine the challenge of different cultures and languages with high productivity
in their scientific work.
Additional and particularly large burdens were taken over by all of the faculty staff of the
institute in order to serve TUB and the scientific community as members or chairmen of
committees on the local, national and international scale, e.g., within advisory or program
committees.
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The reelection of Prof. Christian Thomsen as Dean of the Faculty of Mathematics and Science
in spring 2007 and his devotion for developing multimedia eLearning and eResearch should
be particularly mentioned here.
Finally, the enthusiasm and the dedication of our collaborators at the institute should be
honoured, being fundamental to our success. The key element for future progress of the
institute continues to be their motivation to generate new ideas and to work hard.
This report will
-
give an overview of the formal structure of the institute and list staff and students
-
summarize our teaching activities in order to provide information on our involvement
in the education of young students and scientists
-
summarize the scientific activities of our research groups, including lists of the
approximately 200 scientific papers we published or which have been accepted for
publication within the past 24 months, and of the numerous invited lectures we gave.
Dieter Bimberg
Executive Director
January 2009
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2.
PRIZES AND AWARDS
Particular appreciation of our scientific achievements was expressed by the bestowal of a
number of important awards and prizes:
Dipl.-Phys. Christian Meuer
CHORAFAS-Preis 2007
”Quantum Dot Semiconductor Optical Amplifiers”
The Dimitris N. Chorafas Foundation
Luzern, Switzerland, August 2007
Dipl.-Phys. Robert Seguin
LEOPOLDINA-Preis für junge Wissenschaftler
”Wegweisende Weiterentwicklung der Methode der
ortsaufgelösten Kathodo-Lumineszenz zur
Einzelquantenpunkt-Spektroskopie”
Halle/Saale, Germany, Oktober 2007
Dr. Martin Geller
Carl-Ramsauer-Preis 2007
”Ein quantenpunktbasierter Halbleiterspeicher”
Physikalische Gesellschaft zu Berlin e.V.
Berlin, Germany, November 2007
Dr. Matthias Lämmlin
SANDiE-PhD-Preis 2008
SANDiE-Network of Excellence,
Berlin, Germany, June 2008
Karolin Löser
W.E. Heraeus-Prize 2008 for her excellent and timely
diploma,
Berlin, Germany, July 2008
Dipl.-Phys. Tim D. Germann
Best Poster Award
”Quantum-Dot Semiconductor Disk-Lasers”
at International Nano-Optoelectronics Workshop 2008
Tokyo, Japan, August 2008
Dipl.-Phys. Thomas Bruhn
Dipl.-Phys. Regine Paßmann
Posterpreis der FH Südwestfalen, Deutsche Vakuum
Gesellschaft (DVG) auf der AOFA15 – Arbeitstagung
"Angewandte Oberflächenanalytik", 08.-10.09.2008,
Soest, Germany, October 2008
Dipl.-Phys. Enno Malguth
Feodor Lynen Research Fellowship of the Alexander von
Humboldt foundation,
Berlin, Germany, October 2008
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3.
STRUCTURE AND STAFF OF THE INSTITUTE
3.1
Office of the executive director (01.01.2008)
Prof. Dr. phil. nat. Dieter Bimberg (executive director)
Prof. Dr. rer. nat. Christian Thomsen (deputy executive director)
Prof. Dr. rer. nat. Mario Dähne (deputy executive director)
Prof. Dr. rer. nat. Michael Kneissl (deputy executive director)
Priv.-Doz. Dr. rer. nat. Axel Hoffmann (chief operating officer)
Ines Rudolph (administrative assistant)
3.2
Departments of the institute
Department I:
Prof. Dr. phil. nat. Dieter Bimberg
Department IIa:
Prof. Dr. rer. nat. Christian Thomsen
Prof. Dr. rer. nat. Janina Maultzsch
Department IIb:
Prof. em. Dr.-Ing. Dr. h.c. mult. Immanuel Broser
Priv.-Doz. Dr. Axel Hoffmann
Department III:
Prof. Dr. rer. nat. Mario Dähne
Prof. em. Dr.-Ing. Hans-Eckhart Gumlich
Department IV:
Prof. Dr. rer. nat. Michael Kneissl
Prof. Dr. rer. nat. Wolfgang Richter (retired since 01.04.2005)
3.3
Workshops
Chief operating officer
3.4.1 Mechanical workshop
Werner Kaczmarek (head)
Rainer Noethen
Wolfgang Pieper
Lothar Kroll
Daniela Beiße
3.4.2 Electronic workshop
Norbert Lindner
3.4.3 Glasstechnical workshop
Norbert Zielinski
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3.4
Center of NanoPhotonics
Executive director
Priv.-Doz. Dr. Udo W. Pohl
Chief technology officers
Dr. Friedhelm Hopfer (processing, department I)
Dr. André Strittmatter (epitaxy, department I)
Technical staff
Ilona Gründler (department I)
Dipl.-Krist. Kathrin Schatke (department I)
Dipl.-Ing. Bernhard Tierock (department I)
The Center of Nano-Photonics provides support to the institute departments by growth,
processing, and analysis of materials and structures. Growth facilities are based on metalorganic vapor phase epitaxy (MOCVD). Processing facilities include dry etching, plasma
deposition, and optical lithography. Growth mainly focused on novel quantum dot based
heterostructures. Process development of novel edge and surface emitting devices is pursued.
MOCVD particularly aimed on developping InGaAs-based dots with high areal density for
edge- and surface-emitting lasers. In addition to Stranski-Krastanow growth the novel
approach of cycled sub-monolayer deposition was employed to realize highly efficient gain
media. Both approaches were used to fabricate the first semiconductor disk-lasers (VECSELs)
based on quantum-dots. Devices with features typical for quantum dots like low threshold and
high temperature stability, and a cw output power up to 1.4 W were demonstrated.
Device processing comprised fabrication of VCSELs with oxide mirrors and intracavity
contacts, and narrow ridge-waveguide lasers. Wafers with InGaAs sub-monolayer dots were
processed to efficient VCSELs, which operated at 20 Gb/s between 0°C and 120°C without
current adjustment. Output power exceeding 10 mW was achieved. The concept of photonicband crystal lasers was applied for fabricating ridge-waveguide lasers yielding AlGaAs-based
broad-area quantum-well devices with record high brighness of 3×108 Wcm-2sr-1 and cw
output power of 1.9 W.
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3.5
Affiliated scientific units
3.5.1 Collaborative Research Centre (Sfb 787) of the National Science Foundation DFG
“Semiconductor Nanophotonics: Materials, Models, Devices”
Chairman
Prof. Dr. Michael Kneissl, Institute of Solid State Physics, TU Berlin
Vice chairman
Prof. Dr. Dieter Bimberg, Institute of Solid State Physics, TU Berlin
Board of directors
Prof. Dr. Andreas Knorr, Institute for Theoretical Physics, TU Berlin
Prof. Dr. Klaus Petermann, Department of Electrical Engineering, TU Berlin
Prof. Dr. Jürgen Sprekels, Weierstraß Institut for Applied Analysis and Stochastic
Dipl.-Phys. Tim Germann (until 01.08.2008)
Dipl.-Phys. Ronny Kirste
Administrative assistant
Doreen Nitzsche
Starting in 2008 the new Collaborative Research Centre 787 (Sonderforschungsbereich/SFB
787) "Semiconductor Nanophotonics: Materials, Models, Devices" with an integrated
graduate school was established. Covering the first four years (2008-2011), the Deutsche
Forschungsgemeinschaft (DFG) will support this network with more than 11 million Euros.
Within the planned duration of 12 years the total amount of funding is estimated to be up to
35 million Euros. The SFB 787 combines three complementary research areas: materials,
models and devices to develop novel photonic and nanophotonic devices. In the area of
materials, the research activities are focusing on the material systems GaAs, InP, and GaN
which are the most relevant for photonic devices. Thereby the main objectives are the
investigation of new growth mechanisms as well as the fabrication of integrated
nanostructures like quantum wells, quantum dots and sub-monolayer structures. Based on the
development of new materials and the expertise on the physics of nanostructures we will
investigate, fabricate and characterize a number of novel nanophotonic devices. These
include, e.g. the development of electrically driven, quantum-dot based single photon sources
for quantum cryptography, ultra-fast VCSELs for terabit data communication and high
brilliance lasers from the infrared to the green spectral range. Additionally, edge emitter lasers
and amplifiers for the generation and amplification of ultra-short optical pulses at highest
frequencies will be developed. The interdisciplinary character and the strong educational
networking between the different project partners are important features of the integrated
graduate school. Currently more than 60 Ph.D. students with various scientific backgrounds
ranging from mathematics, physics to electrical engineering are members of the graduate
school. Another goal of the integrated graduate school is to encourage the participation of
female students in the area nanophotonics and to support them in their scientific careers. The
SFB 787 is comprised of a total of 16 projects from six institutions: The Technische
Universität Berlin (Chair University), the Humboldt Universität zu Berlin, the Otto-von-
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Guericke-Universität Magdeburg as well as the Ferdinand-Braun-Institut für
Höchstfrequenztechnik, the Fraunhofer Institut für Nachrichtentechnik (Heinrich-HertzInstitut), the Weierstraß-Institut für Angewandte Analysis und Stochastik and the KonradZuse-Zentrum für Informationstechnik.
3.5.2 Association of German Nanotechnology Centers of Competence - AGeNT-D:
Arbeitsgemeinschaft der Nanotechnologie-Kompetenzzentren Deutschlands
Chairman
Prof. Dr. Dieter Bimberg
Steering committee
Dr. Andreas Baar (NMN e.V.)
Hr. Alexander Bracht (Hessen NT)
Prof. Harald Fuchs (CeNTech)
Prof. Wolfgang Heckl (ENNaB)
Dr. Regine Hedderich (NanoMat)
Dr. Andreas Leson (UFS)
Prof. Frank Löffler (UPOB e.V.)
Prof. Michael Veith (NanoChem e.V.)
Prof. Roland Wiesendanger (INCH)
Prof. Christiane Ziegler (NanoBioNet e.V.)
Dr. Sven Rodt
Doreen Nitzsche
AGeNT-D is the German network of nanotech clusters. It comprises nine competence centres
and two nanotech networks from all over Germany to cover the whole spectrum of
nanotechnology. AGeNT-D promotes R&D, creates synergies and increases national and
international visibility of nanotechnology in Germany.
3.5.3 National Competence Center on NanoOptoelectronics of the Federal Ministry of
Education and Research (bmb+f) - NanOp
Chairman
Prof. Dr. Dieter Bimberg
Steering committee
Prof. Alfred Forchel (U Würzburg)
Dr. Norbert Grote (HHI FhG)
Dr. Klaus Schulz (Merge Optics)
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Dr. Sven Rodt
Doreen Nitzsche
NanOp is the German national network for the application of lateral nanostructures,
nanoanalytical techniques and optoelectronics. It unites 44 nationally and internationally
leading research and development groups, technical and venture capital companies from
Germany and the A. F. Ioffe Institute from St. Petersburg, Russia.
NanOp has two goals: to speed up research and development in the field of nanotechnologies
for Optoelectronics and to transfer the results to production.
3.5.4 Multimedia Center for eLearning and eResearch (MuLF)
Executive director
Prof. Dr. rer. nat. Sabina Jeschke
Staff
Dr. Lars Knipping
Dipl.-Phys. Mark Wilke
Dipl.-Phys. Dirk Heinrich
Dipl.-Math.Olivier Pfeiffer
Dipl.-Math. Gerald Lach
Dipl.-Math. Robert Luce
Dipl.- Inf. (FH) Michael Jeschke
Dipl.-Inf. Uwe Sinhar
Dipl.-Chem. Tilman Rassy
cand. Dipl.-Phys. Carola Nisse
cand. Dipl.-Inf. Mario Wegner
Sabine Morgner
The Multimedia Center for Eteaching and Eresearch (MuLF) as a center in our faculty is
responsible for central tasks in the area of information technology-based support of teaching.
Achievements are, e.g., the information system for students (ISIS), the introduction of
electronic chalk, the management system for examinations (MOSES), the electronic eprint
server, or the electronic management system for the "Lange Nacht der Wissenschaften".
Severeal thousand of students across the university are using these services. MuLF advises
newcomers to Eteaching and offers training for the optimal use of the new media at
university. Furthermore, MuLF coordinated the multimedia equipment in the lecture rooms at
the university. Scientifically the center coordinates projects, like, e.g., Nemesis, a large
university-wide teaching and research project.
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3.6
External and retired faculty members of the institute
S-Prof. Dr. Norbert Esser, Institute for Analytical Sciences (ISAS) Berlin
apl. Prof. Dr. Rudolf Germer, University of Applied Sciences (FHTW) Berlin
apl. Prof. Dr. Holger Grahn, Paul-Drude-Institute (PDI) Berlin
Priv.-Doz. Dr. Thorsten U. Kampen, Fritz-Haber-Institute (FHI) Berlin
S-Prof. Dr. Bella Lake, Hahn-Meitner-Institute (HZB) Berlin (since 01.08.2006)
apl. Prof. Dr. Hans-Joachim Lewerenz, Hahn-Meitner-Institute (HZB) Berlin
apl. Prof. Dr. Michael Meißner, Hahn-Meitner-Institute (HZB) Berlin
Priv.-Doz. Dr. Norbert Nickel, Hahn-Meitner-Institute (HZB) Berlin
Priv.-Doz. Dr. Harm-Hinrich Rotermund, Fritz-Haber-Institute (FHI) Berlin
Priv.-Doz. Dr. Konrad Siemensmeyer, Hahn-Meitner-Institute (HZB) Berlin
S-Prof. Dr. Michael Steiner, Hahn-Meitner-Institute (HZB), Berlin
S-Prof. Dr. Alan Tennant, Hahn-Meitner-Institute (HZB) Berlin
apl. Prof. Dr. Wolfgang Treimer, University of Applied Sciences (TFH) Berlin
3.7
Honorary, adjunct and guest professors, Humboldt awardees and fellows
Prof. Dr. Alexander M. Bradshaw, executive director, Max-Planck-Institut für Plasmaphysik
München, Germany, Honorary Professor
Prof. Dr. Gadi Eisenstein, Technion – Israel Institute of Technology, Haifa, Israel,
Humboldt Awardee
Prof. Dr. Vladimir Gaysler, Russian Academy of Sciences, Novosibirsk, Russia,
Guest Professor
Dr. Leonid Karachinsky, A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia,
Humboldt Fellow
Dr. Jungho Kim, National University, Seoul, Republic of Korea, Marie Curie Fellow
Prof. Dr. Nicolai N. Ledentsov, A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia,
Guest Professor
Dr. Vitali A. Shchukin, A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia,
DLR Fellow, Humboldt Fellow
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4.
FOREIGN GUESTS
Department I
Esma Ahlatcioglu, Istanbul University, Turkey
19.06.-30.09.2008
M.Sc. Namik Akçay, Istanbul University, Turkey
16.02.-15.11.2007
M.Sc. Amélia Ankiewicz, University of Aveiro, Portugal
28.08. -14.09.2007 and 13.-26.01.2008
Yvonne Beyer, University of Cambridge, U.K.
09.07.-07.09.2007
Dr. Sergey Blokhin, A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia
23.10.-20.12.2008
Prof. Dr. Alexei L. Efros, University of Utah, Salt Lake City, USA
30.07.-05.08.2007
Dr. Leonid Karachinsky, A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia
01.01.-31.12.2007 and 11.08.-25.10.2008
Hadrien Lepage, Engineering Physics School, Grenoble, France
01.10.-10.12.2007
Dr. Innokenty Novikov, A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia
07.04.-28.06.2008
Prof. Dr. Nurten Öncan, Istanbul University, Turkey
15.02.-02.03.2007 and 15.06.–16.07.2007
Erwan Varene, Université de Rennes 1, France
04.02.-30.06.2008
Department II
M. Sc. Sofia Theodoropoulou, National Technical University of Athens, Greece
15.-30.04.2006
Dr. Detlev Hofmann, Justus-Liebig-Universität Gießen, Germany
06.-07.02.2007
Dr. Jos Haverkort, Eindhoven University of Technology, Eindhoven, The Netherlands
24.-28.04.2007
Prof. Dr. Sergey Maksimenko, Belarusian State University, Minsk, Belarus
01.06.-31.07.2007, 03.-24.12.2007, 01.06.-31.07.2008, 08.-31.12.2008
Dr. Gregory Slepyan, Belarusn State University, Minsk, Belarus
01.06.-31.07.2007, 03.-24.12.2007, 01.-31.07.2008
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Prof. Dr. Oleg Kibis, State Technical University, Novosibirsk, Russia
01.06.-31.07.2007, 01.06.-31.07.2008
Prof. Dr. Matthew Philips, University of Technology, Sydney, Australia
24.-28.09.2007
Prof. Dr. Herbert Willi Kunert, University of Pretoria, South Africa
01.-31.12.2007, 01.-24.06.2008, 17.-30.11.2008
Prof. Dr. Nikolaus Dietz, Georgia State University, Atlanta, USA
14.-30.12.2007, 25.05.-05.06.2008
Prof. Dr. Zlatko Sitar, North Carolina State University, Raleigh, USA
18.-22.12.2007
Dr. Ian Ferguson, Georgia Institute of Technology, Atlanta, USA
28.-31.05.2008
Prof. Dr. Bruno K. Meyer, Justus-Liebig-Universität Gießen, Germany
05.-08.06.2008
Prof. Dr. Shigefusa Chichibu, Tohoku University, Minsk, Belarus
01.-31.07.2008
Dr. Anna Rodina, Ioffe Physical Technical Institute, St. Petersburg, Russia
06.-26.08.2008
Prof. Dr. Tadeusz Suski, Unipress, Warschau, Poland
03.-04.11.2008
Prof. Dr. John Robertson, University of Cambridge, United Kingdom
09.-16.11.2008
Lucas R. Muniz, Institut de Ciencia de Materials de Barcelona, Spain
19.-28.11.2008
Juan S. Reparaz, Institut de Ciencia de Materials de Barcelona, Spain
19.11.-03.12.2008
Department III
Eric Huwald, LaTrobe University, Australia
23.07.-12.08.2007
Petar Stojanov, LaTrobe University, Australia
16.07.-11.08.2007, 04.-16.10.2007, 20.07.-03.08.2008, 03.-16.11.2008
Pablo Sanchez Bodega, Fritz-Haber-Institut, Berlin, Germany
20.12.2007
Prof. Dr. John D. Riley, LaTrobe University, Australia
04.-16.02.2008
PD Dr. Philipp Ebert, Forschungszentrum Jülich, Germany
31.03.-04.04.2008, 17.-20.06.2008, 31.08.-05.09.2008, 12.-17.10.2008,
09.-12.12.2008
23
Svetlana Borisova, Forschungszentrum Jülich, Germany
31.03.-04.04.2008
Stefan Ulrich, Fritz-Haber-Institut, Berlin, Germany
19.06.2008
Department IV
Dr. Sandhya Chandola, Trinity College, Dublin, Irland
01.01. -31.12.2008
Dr. Peter Kiesel, Palo Alto Research Center (PARC), Palo Alto, USA
19.04. -21.04.2007
Ph.D. Dott. Roberto Jakomin, Unitersitá degli studi di Parma, Italy
01.01.2007-31.10.2007
Prof. Dimitra Papadimitriou, National Technical University of Athens (Ethniko Metsovio
Polytechnio), Athinai (Athen), Greece,
01. -21.02.2007, 29.07.-25.08.2007
Prof. Dr. Arnab Bhattacharya, Tata Institute of Fundamental Research, Mumbai, India
07. -15.06.2007
Dr. Eugen Speiser, Roma II (Tor Vergata), Dipartimento di Fisica, Rome, Italy,
11.-23.02.2008
Prof. Dr. Dimitra Papadimitriou, National Technical University of Athens (Ethniko Metsovio
Polytechnio), Athinai (Athen), Greece,
16.02. -01.03.2008
Prof. Ilias Zouboulis, National Technical University of Athens, Greece,
17.03.2008
Prof. Shiro Tsukamoto, Anan National College of Technology, Tokushima, Japan,
29.-31.05.2008
Prof. Tomoya Konishi, Anan National College of Technology, Tokushima, Japan,
29.-31.05.2008
Silvano Dell Gobbo, Roma II (Tor Vergata), Dipartimento di Fisica, Rome, Italy,
24.05. -05.06.2008
24.05. -05.06.2008
Prof. Dr. Arnab Bhattacharya, Tata Institute of Fundamental Research, Mumbai, India,
25.05. -08.06.2008
M.Sc. Abdul Kadir, Tata Institute of Fundamental Research, Mumbai, India,
24.05. -15.07.2008
M.Sc. Neysha Lobo, Tata Institute of Fundamental Research, Mumbai, India,
24.06. -04.07.2008
24
Prof. Dimitra Papadimitriou, National Technical University of Athens (Ethniko Metsovio
Polytechnio), Athinai (Athen), Griechenland,
10.-31.08.2008
11.-24.08.2008
Prof. Ali Saeed Al-Ghamdi, King Saud University, Riyadh, Saudi Arabia,
14.01.2008
Ph.D. Abdullah A. Al-Othman, King Saud University, Riyadh, Saudi Arabia,
14.01.2008
Dr. Yussuf M. Al-Jindan, King Faisal University, Al-Ahsa, Saudi Arabia,
14.01.2008
Prof. Dr. rer. Nat Agus Rubiyanto, Education Attaché, Embassy of the Republic of Indonesia,
Berlin,
04.11.2008
Dr.-Ing. Yul Y. Nazaruddin, Education Attaché, Embassy of the Republic of Indonesia,
Berlin,
04.11.2008
Ph.D. Hermawan K. Dipojono, Institut Teknologi Bandung, Bandung, Indonesia,
04.11.2008
Dr. Nurul Taufiqu Rochman, Indonesian Institute of Sciences, Puspiptek, Indonesia,
04.11.2008
Dr. Ariel Felipe, Scientific Advisor Office, Council of The State Republic of Cuba, Habana,
Cuba,
22.09.2008
Roberto Infante, Commercial Council, Embassy of the Republic of Cuba, Berlin,
22.09.2008
Prof. Weng Chow, Sandia National Laboratories, Albuquerque, USA,
12.09.-11.10.2008
17.-27.11.2008
M.Sc. Dinh van Duc, SKKU Advanced Institute of Nanotechnology (SAINT),
Sungkyunkwan University, Cheoncheon-dong, Korea,
13.-21.12.2008
25
4.1
Talks by Guests
Department I
Dr. Tomoyuki Akiyama
Recent progress in quantum dot semiconductor
amplifiers at long wavelength
18.09.2007
Fujitsu, Tokyo, Japan
Dr. Paola Atkinson
Site control of InAs quantum dots
13.07.2007
Max-Planck-Institut für Festkörperforschung, Stuttgart,
Germany
Kambiz Behfar
Vertical external cavity surface emitting lasers
for the MIR
04.07.2008
Philips Research Labs, Aachen, Germany
Prof. Dr. Jozef T. Devreese
Polarons and the optical spectra of quantum dots:
Effects of non-adiabaticity
26.05.2008
Laboratorium Theoretische Fysica van de Vaste Stoffen,
Universiteit Antwerpen, Belgium
Prof. Russell D. Dupuis
High-brightness green light-emitting diodes
for solid-state lighting applications
25.10.2007
Georgia Institute of Technology, Atlanta, USA
Prof. Alexei L. Efros
Problem of subwavelength imaging by Veselago lens
02.08.2007
University of Utah, Salt Lake City, USA
Dr. Thomas Hannappel
Grenzflächenuntersuchungen
für hocheffiziente Solarzellen
22.10.2007
Hahn-Meitner-Institut, Berlin, Germany
Prof. James Harris
Progress and challenges of GalnNAsSb
for optical communication
18.09.2007
University Stanford, USA
Christian Junge
Photonenkorrelation bei der optischen parametrischen
Oszillation - Konzept für eine Zwei-Photonenquelle
19.12.2008
Technische Universität Darmstadt, Germany
26
Dr. Vladimir Kalosha
High-power lasers with ultra-narrow vertical beam
divergence based on longitudinal photonic bandgap
crystal: Concept, design, and performance
characterization
12.08.2008
University of Ottawa, Canada
Prof. Dr. Ruben P. Seisyan
Extreme ultra violet & soft X-ray lithography as an
universal instrument of nanotechnologies and
nanoelectronics
24.11.2008
A.F. Ioffe Physico-Technical Institute St. Petersburg, Russia
Department II
Prof. Dr. Ian Ferguson
Understanding GaN-based Room Temperature
Spintronics
29.05.2008
Georgia Institute of Technology, Atlanta, USA
Prof. Dr. Andreas Hirsch
Synthese und supramolekulare Organistion von
kohlenstoffreichen Architekturen
03.12.2008
Universität Erlangen-Nürnberg, Germany
Lucas Cerioni
Grundlagen und Anwendung der NMR-Spetroskopie
16.12.2008
Univerisidad National de Córdoba, Argentina
Prof. Dr. Shigefusa F. Chichibu Growth issues and optical properties of nonpolar
(Al,In,Ga)N films and quantum wells
16.12.2008
Tohoku University, Japan
Department III
Eric Huwald
The LaTrobe Toroidal Analyzer
26.07.2007
LaTrobe University, Australia
Pablo Sanchez Bodega
Imaging and Control of Surface Reactions
20.12.2007
Fritz-Haber-Institut, Berlin, Germany
Stefan Ulrich
Pd and Au atoms on SiO2/Mo(112)
19.06.2008
Fritz-Haber-Institut, Berlin, Germany
27
Petar Stojanov
Gold overlayers on silicon carbide - a novel system for
low-dimensional structures
13.11.2008
LaTrobe University, Australia
Department IV
Dr. Peter Kiesel
Native fluorescence spectroscopy on-a-chip
19.04.2007
Palo Alto Research Center, USA
Prof. Dr. Arnab Bhattacharya
MOVPE growth of InN materials
07.06.2007
Tata Institute of Fundamental Research, Mumbai, India
Prof. Dr. Joachim Wagner
Halbleiterlaser und Leuchtdioden auf der Basis der
Gruppe III-Nitride und –Antimonide
31.10.2007
Fraunhofer Institut für Angewandte Festkörperphysik,
Freiburg, Germany
Heiko Schäfer
Komponenten und Anwendungen für
applikationsspezifische Lab-on-Microchips
07.01.2008
Institut für Mikrosystemtechnik, Universität Siegen,
Germany
Dr. Neelima Paul
Fabrication and characterization of Si/Ge nanostructures
using STM
09.04.2008
Forschungszentrum Jülich, Germany
Prof. Dr. Arnab Bhattacharya
From Nitrides to Nanowires: III-Vs research at TIFR
28.05.2008
Prof. Shiro Tsukamoto
InAs quantum dot evolution observed by in-situ scanning
tunnelling microscopy during molecular beam epitaxy
growth
30.05.2008
Anan National College of Technology, Tokushima, Japan
Prof. Tomoya Konishi
Investigation on high catalytic activity mechanism of
organopalladium catalyst on S-terminated GaAs(001)(2x6) surface
30.05.2008
Anan National College of Technology, Tokushima, Japan
28
Dipl.-Phys. Abdul Kadir
MOVPE-grown InN: structural and low temperature
transport properties
25.06.2008
M. Sc. Neysha Lobo
Photothermal Deflection Spectroscopy of MOVPE-grown
GaN epilayers
27.06.2008
Prof. Weng Chow
Microscopic theory and is application in semiconductor
laser development
25.09.2008
Sandia National Laboratories, Albuquerque, USA
M. Sc. Dinh van Duc
Synthesis, structural analysis and field emission
properties of GaN nanostructures
17.12.2008
SKKU Advanced Institute of Nanotechnology (SAINT),
Sungkyunkwan University, Cheoncheon-dong, Korea
29
5.
PARTICIPATION IN COMMITEES
5.1
Program and Advisory Committee
Dieter Bimberg
Member of the Steering Committee of the “6th Int. Conf. on Low Dimensional Structures and
Devices” (LDSD 2007) San Andrés, Columbia, April 16 - 20, 2007
Member of the AIXTRON Young Scientist Award Committee at the “15th Int. Symp.:
Nanostructures: Physics and Technology”, Novosibirsk, Russia, June 25 - 29, 2007
Member of the International Advisory Committee of the “Int. Conf. on Electronic Properties
of Two-dimensional Systems and Modulated Semiconductor Structures”,
Genova, July 15 - 20, 2007
Member of Program Committee of the “7th IEEE Int. Conf. on Nanotechnology”, Hong Kong,
SAR, China, August 2 - 5, 2007
Member of the International Advisory Committee of “11th Int. Conf. on the Formation of
Semiconductor Interfaces” (ICFSI-11), Manaus, Amazonas, Brazil, August 19 - 24, 2007
Member of the Program Committee of the “Int. Symp. on Compound Semiconductors”
(ISCS), Kyoto, Japan, October 14 - 20, 2007
Member of the International Advisory Committee of “2007 Virtual Conf. on Nanoscale
Science and Technology” (C-NST), Fayetteville, Arkansas, USA, October 21 - 25, 2007
Member of the Steering Committee of “Aus- und Weiterbildung in
Hochtechnologiefeldern”(AWNET), Berlin, Germany, November 29 - 30, 2007
Member of the International Advisory Committee of the “Workshop on Recent Advances in
Low Dimensional Structures and Devices”, Nottingham, UK, April 7 - 9, 2008
Member of the Program Committee of the conference “Semiconductor Lasers and Laser
Dynamics III” at “Photonics Europe 2008”, Strasbourg, France, April 7 - 11, 2008
Member of the International Advisory Committee of the “Int. Conf. on Superlattice,
Nanostructure and Nanodevices” (ICSNN-2008), Natal, Brazil, August 3 - 8, 2008
Member of the Technical Program Committee of the “IEEE Nano 2008 Conference”,
Arlington, TX, USA, August 18 - 21, 2008
Member of the International Program Committee of “Nanotechnology and Applications
((NANA 2008) Crete, Greece, September 29 - October 1, 2008
Member of the International Advisory Committee of “Rusnanotech: Nanotechnology
International Forum”, Moscow, Russia, December 3 - 5, 2008
30
Axel Hoffmann
Member of the Program Committee of the “SPIE Photonics West”, San Diego, California,
USA, January 2007
Member of the Organisation Committee of the “SANDiE Optics Task Force Meeting”, Berlin,
Germany, January 2007
Member of the Program Committee of the “Frühjahrstagung der Deutschen Physikalischen
Gesellschaft (DPG)”, Dresden, Germany, March 2007
Member of the Program Chair of the “ICNS-7 The Seven’th International Conference On
Nitride Semiconductors”, Las Vegas, USA, August 2007
Member of the Organisation Committee of the “SANDiE Optics Task Force Meeting”, Berlin,
Germany, January 2008
Member of the Program Committee of the “SPIE Photonics West”, San Jose, California,
USA, January 2008
Member of the Program Committee of the “Frühjahrstagung der Deutschen Physikalischen
Gesellschaft (DPG)”, Berlin, Germany, March 2008
Advisory Committee of the “7’th International Symposium on Semiconductor Light Emitting
Devices (ISSLED)”, Phoenix, USA, April 2008
Member of the Advisory Committee of the “International Workshop on Nitride
Semiconductors (IWN)”, Montreux, Switzerland., October 2008
Michael Kneissl
Member of the Program Committee of the “SPIE Photonics West Conference 2007”,
Symposium on “Novel in-plane semiconductor lasers”, San Jose, USA, January 2007
Member of the Program Committee of the “International Workshop on Nitride
Semiconductors” & Chairman of Workshop 6 “Technology and Devices”, IWN 2008,
Montreux, Switzerland, September 2008
Member of the Program Committee of the “SPIE Photonics West Conference 2008”,
Symposium on “Novel in-plane semiconductor lasers”, San Jose, USA, January 2008
Member of the Organizing Committee of the “E-MRS Fall Meeting 2009”, Symposium on
“InN material and alloys”, Warsaw, Poland, September 2009
Chairman of the Organizing Committee, DGKK Workshop "Epitaxie von III/V Halbleitern",
2009, Berlin, Germany, December 2009
Nikolai Ledentsov
Member of the Program Committee of the conference “Physics and Simulation of
Optoelectronic Devices XV”, OPTO 2007, Photonics West, San José, California, USA,
January 20 - 25, 2007
31
Udo Pohl
Member of the Program Committee of the “Int. Workshop on Long Wavelength Quantum
Dots”, Rennes, France, July 5 - 6, 2007.
Sven Rodt
Chair of the session: ‘Excitons & Plasmons’ at the “8th Int. Conference on Physics of LightMatter Coupling in Nanostructures” (PLMCN8), Tokyo. Japan, April 7 - 11, 2008
Christian Thomsen
Organiser and member of the committee: “Electronic Properties of Novel Materials”,
Kirchberg, Austria, March 10 - 17 2007
Organiser and member of the committee: “Electronic Properties of Novel Materials”,
Kirchberg, Austria, February 29 - March 8 2008
32
33
5.2 Editorial duties / Boards of institutes and companies
Dieter Bimberg
Scientific Advisory Board, PBC Lasers Ltd., Kibbutz Einat, Israel
International Editorial Advisory Board "Opto-Electronics Review" (O-ER) Warsaw, Poland
Editorial Board, IET Optoelectronics Journal, U.K.
Editorial Board, “Research Letters in Physics”, USA/Egypt
International Board of Editors, “Semiconductor News”, Pakistan
Member of the 2007 and 2008 LEOS “William Streifer Scientific Achievement Award”
Committee
Chairman Scientific Advisory Board, V. I. Systems GmbH, Berlin, Germany
Chairman of the Board, PBC Lasers GmbH, Berlin, Germany
Axel Hoffmann
Editorial Board of “physica status solidi (c)”, WILEY-VCH, Weinheim, Germany
Markus Pristovsek
Guest editor for the IC MOVPE Proceedings 2008, Journal of Crystal Growth, Elsevier
Christian Thomsen
Editorial board of physica status solidi (b) and (c)
President of the Physikalische Gesellschaft zu Berlin e.V. (2006-2008)
Editor Solid State Communications
34
35
6.
EXTERNAL COLLABORATIONS
Department I
Universiteit Antwerpen, Belgium, Prof. J.T. Devreese, Prof. F. Peeters, Prof. V.M. Fomin
National Technical University, Athens, Greece, Prof. D. Papadimitriou
Universidad de Aveiro, Portugal, Prof. N. Sobolev
Humboldt Universität zu Berlin, Germany, Prof. O. Benson, Prof. R. Zimmermann
University of Cambridge, U.K., Prof. I. White, Prof. R. Penty
University of Cardiff, U.K., Dr. P. Borri
Bookham Ltd., Caswell, U.K., Dr. M. Wall
University of Cincinnati, Ohio, USA, Prof. H.-P. Wagner
University of Cork, Tyndall Center, Ireland, Prof. E. O’Reilly, Prof. P. Townsend
Universität Dortmund, Germany, Prof. U. Woggon,
Qimonda GmbH, Dresden, Germany, Dr. C. Ludwig
Technische Universiteit Eindhoven, The Netherlands, Prof. M. Kœnrad
University of Central Florida, USA, Prof. D.G. Deppe
Technische Universität Bergakademie Freiberg, Germany, Prof. T. Mikolajick
Universität Karlsruhe, Germany, Prof. D. Gerthsen
University of Lancaster, U.K., Prof. M. Hayne
Universität Leipzig, Germany, Prof. M. Grundmann
Katholieke Universiteit Leuven, The Netherlands, Prof. V. Moshchalkov
Universität Linz, Austria, Prof. G. Bauer, Dr. A. Darhuber
Lund University, Sweden, Prof. L. Samuelson
Universität Magdeburg, Germany, Prof. J. Christen, Prof. A. Krost
University of Michigan, USA, Prof. P.K. Bhattacharya
University of Nottingham, U.K., Prof. L. Eaves, Dr. M. Henini
Institute of Semiconductor Physics, Novosibirsk, Russia, Prof. V.A. Gaysler
Osram Opto Semiconductor GmbH, Regensburg, Germany, Dr. C. Fricke
University of Ottawa, Canada, Dr. M.V.P. Kalosha
INTEL, Santa Clara, USA, Dr. B. Caparo, Dr. I. Young, Dr. C. Krautschik
University of Sheffield, U.K., Prof. M. Skolnick, Prof. D. Mowbray
A.F. Ioffe Physico-Technical Institute and St. Petersburg Center of Research and Education of
RAS, St. Petersburg, Russia, Prof. Zh. I. Alferov, Prof. V.M. Ustinov
KTH Stockholm, Sweden, Prof. L. Thylen
University of Tampere, Finland, Prof. O. Okhotnikov, Prof. M. Pessa
The University of Tokyo, Japan, Prof. Y. Arakawa
Tokyo Institute of Technology, Japan, Prof. T. Kamiya
36
Department II
Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany, Dr. Siegmar Roth
Centro Atomico, Bariloche, Argentinia, Prof. Dr. Alex Fainstein
Forschungszentrum Karlsruhe, Dr. Frank Hennrich
Forschungszentrum Karlsruhe, Dr. Ralph Krupke
University of Cambridge, Prof. Dr. John Robertson
Freie Universität Berlin, Prof. Dr. Stephanie Reich
University of Technology Sydney, Australia, Dr. Matthew Phillips
Belarus State University, Minsk, Belarus, Dr. M. V. P. Kalosha
Institute for Nuclear Problems, Minsk, Belarus, Prof. S. Maksimenko, Dr. G. Ya. Slepyan
CNRS Université Montpellier, France, Prof. B. Gil, Dr. B. Daudin
Aixtron AG, Aachen, Germany, Priv. Doz. Dr. M. Heuken
Universität Gießen, Germany, Prof. B.K. Meyer
Otto-von-Guericke Universität, Magdeburg, Germany, Prof. J. Christen
OSRAM Opto Semiconductors GmbH, Regensburg, Germany, Dr. C. Fricke
Walter Schottky Institut München, Germany, Prof. M. Stutzmann
University of Tokyo, Japan, Prof. Yasuhiko Arakawa
Mie University, Japan, Prof. K. Hiramatsu
A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia, Prof. Zh.I. Alferov
Novosibirsk State Technical University, Russia, Prof. O. V. Kibis
Universidade de Aveiro, Portugal, Prof. Nikolaus Sobolev
Instituto de Cienca de materiales, Consejo, Barcelona, Spain,
Prof. Dr. Alejandro Goñi, Prof. Dr. Pablo Ordejón
University of Pretoria, South Africa, Prof. Dr. Herbert Willi Kunert
University of Exceter, United Kingdom, Dr. A. Plaut, Dr. M. E. Portnoi
National Center for Electron Microscopy, Berkley, California, USA, Dr. Christian
Kieselowski
Georgia State University, Atlanta, USA, Prof. Dr. Nikolaus Dietz
School of Materials Science and Engineering, Georgia Institute of Technology Atlanta, USA,
Prof. I. T. Ferguson
North Carolina State University, Raleigh, USA, Dr. James L. Oblinger
Massachusetts Institute of Technology, Cambridge, USA, Prof. Dr. Stephanie Reich
North Carolina State University, Raleigh, USA, Prof. Dr. Zlatko Sitar
37
Department III
Carnegie-Mellon University, Pittsburgh, USA, Prof. R.M. Feenstra
Ferdinand-Braun-Institut für Hochfrequenztechnik, Berlin, Germany, PD Dr. M. Weyers, Dr.
P. Crump
Forschungszentrum Jülich, Germany, PD Dr. P. Ebert
Fraunhofer-Institut für Nachrichtentechnik - Heinrich-Hertz-Institut, Berlin, Germany, Dr. H.
Künzel
Freie Universität Berlin, Germany, Prof. G. Kaindl
Fritz-Haber-Institut, Berlin, Germany, Prof. K. Horn, Prof. K. Jacobi, Prof. M. Scheffler
Helmholtz-Zentrum Berlin für Materialien und Energie, Germany, Dr. S. Sadewasser
LaTrobe University, Australia, Prof. J.D. Riley, E. Huwald, P. Stojanov
Max-Planck-Institut für Fertkörperforschung, Stuttgart, Germany, Dr. O.G. Schmidt, Prof. K.
Kern
Paul-Drude-Institut, Berlin, Germany, Dr. L. Geelhaar, Prof. H. Riechert
Technische Universität Dresden, Germany, Prof. C. Laubschat, Dr. S.L. Molodtsov, Dr. D.
Vyalikh
Universität Magdeburg, Germany, Prof. A. Krost
Universität Marburg, Germany, PD Dr. K. Volz, Prof. W. Stolz
University of Cambridge, United Kingdom, I. Farrer, Prof. D. A. Ritchie
University of New Mexico, USA, Prof. D. Huffaker, Dr. G. Balakrishnan
University of Sheffield, United Kingdom, Prof. M. Hopkinson
University of Texas, Austin, USA, Prof. C.K. Shih
Department IV
Aixtron AG, Aachen, Germany, Prof. Dr. M Heuken,
Alcatel Thales III-V Lab, Marcoussis, France, Dr. Marie Antoinette di Forte Poisson
Anan National College of Technology, Tokushima, Japan, Prof. Tomoya Konishi
BESSY Berlin, Germany, Dr. Walter Braun,
CNRS, Délégation de Normandie, France, Dr. Pierre Ruterana
DELTA (Dortmunder ELekTronenspeicherring-Anlage), Zentrum für Synchrotronstrahlung,
Technische Universität Dortmund, Germany, Prof. Dr. Karsten Westphal
Ecole Polytechnique Fédérale de Lausanne, Switzerland, Prof. Dr. N. Grandjean
ETH Zürich, Integrated Systems Laboratory, Switzerland, Prof. Dr, Bernd Witzigmann
Ferdinan-Braun-Institut für Höchstfrequenztechnik, Berlin, Germany, Prof. Dr. G. Tränkle
Fraunhofer Instite for Applied Solid State Physics (IAF), Freiburg, Germany, Prof. Dr.
Wagner
Friedrich-Schiller-Universität, Jena, Germany, Prof. Dr. Friedhelm Bechstedt
Institute for Analytical Sciences, Berlin and Dortmud, Germany, Prof. Dr. N. Esser
Kompetenzzentrum Wasser Berlin, Berlin, Germany, Dr. Boris Lesjean
LayTec GmbH, Berlin, Germany, Dr. T. Zettler
National Technical University, Athens, Greece, Prof. Dr. Papadimitriou
38
Norwegian University of Science and Technology, Trondheim, Norway, Prof. B.O. Fimland
NUSOD Institute LLC, Newark, USA, Prof. Dr. J. Pipirek
Osram Opto Semiconductors GmbH, Regensburg, Germany, Dr. H.-J. Lugauer
Otto-von-Guericke University Magdeburg, Institute of Experimental Physics, Magdeburg,
Germany, Prof. Dr. J. Christen & Prof. Dr. A. Krost
Palo Alto Research Center, Califonia, USA, Dr. Noble M. Johnson
Philips Research, Eindhoven, The Netherlands, Dr. Ruud Balkenende
Sandia National Laboratories, Albuquerque, New Mexcio, USA, Prof. Weng Chow
Semiconductor Technology Research, Inc. (STR), Richmond, USA, Dr. S.U. Karpov
Sungkyunkwan Universtiy, Suwon Korea, Rep. Südkorea, Duc van Dinh
Tata Institute of Fundamental Research, Tokushima, India, Prof. Dr. Bhattacharya
Technische Universität Ilmenau, Germany, Dr. Ruediger Goldhahn
Thomas Swan Scientific Equipment Ltd., Consett, UK, Dr. Bernd Schulte
Trinity College, The University of Dublin, Irland, Prof. John Mc Gilp
TU Braunschweig. Institute of Applied Physics, Prof. Dr. A. Hangleiter
Ulm University, Institute of Optoelectronics, Prof. Dr. F. Scholz
Universidade Federal do ABC, Santo Andre, Brazil, Prof. Dr. Ronei Mioto
Università degli studi di Parma, Italy, Prof. L. Tarricone
Università degli Studi di Roma II "Tor Vergata", Italy, Prof. Dr. Wolfgang Richter
Universitad Politecnica de Madrid, Spain, Dr. M.A. Sanchez-García
Universität Göttingen, IV. Physikalisches Insitut, Germany, Dr. Martin Wenderoth
Universität Paderborn, Germany, Prof. Dr. Gero Schmidt
Universität Stuttgart, Institut für Halbleiteroptik und Funktionelle Grenzflächen, Germany,
Prof. Dr. P. Michler, Dr. M. Jetter
Universität Stuttgart, Institut für Strahlwerkzeuge (IFSW), Dr. U. Brauch
University of Bologna, Italy, Prof. Anna Cavallini
University of Liverpool, UK, Prof. Dr. Peter Weightman, Dr. D. Martin
University of Strathclyde, Glasgow, UK, Dr. Carol Trager-Cowan
University of Warwick, UK, Prof. Chris McConville
University Regensburg, Inst. of Experimental and Applied Physics, Germany, Dr. U. Schwarz
Yale University, New Haven, USA, Prof. Dr. Richard K. Chang
Veolia Water, Anjou Recherche, Drinking Water & Membranes Technologies Dept.,
Maisons-Laffitte, France, Florencio Martin
39
7.
TEACHING
Internal faculty members
Selected Topics of Solid State Physics
D. Bimberg, C. Thomsen, M. Kneissl
Applied Physics I + II
D. Bimberg, U.W. Pohl, A. Hoffmann, M. Weyers
Seminar on Photonics: Materials, Devices, Systems
D. Bimberg, A. Hoffmann, F. Hopfer, U.W. Pohl, A. Strittmatter
Lab Course in Methods of Applied Physics I and II
D. Bimberg
Lab Course in Advanced Experimental Physics
D. Bimberg, M. Dähne, A. Hoffmann, C. Thomsen, M. Kneissl
Semiconductor Epitaxy
U. W. Pohl
Experimental Physics I + II
M. Dähne
Experimental Physics V
M. Dähne
Seminar on Surfaces, Interfaces and Nanostructures
M. Dähne, H. Eisele, J. Grabowski, L. Ivanova, A. Lenz, R. Timm, M. Wanke
Physics for Chemists and Food Chemists
R. Timm
Introduction to the Basics of Magnetic Resonance Spectroscopy
W. Gehlhoff
Macroscopic Quantum Phenomena in Solid State Physics
A. Hoffmann
Modern Methods of Solid State Physics
A. Hoffmann
Solid State Physics I + II
M. Kneissl, P. Vogt, M. Pristovsek
Lab Course in Solid State Physics I + II
M. Kneissl, P. Vogt, M. Pristovsek
Seminar series “Physics of Semiconductor Interfaces and Heterostructures”
M. Kneissl, W.Richter, P .Vogt
Seminar series “Modern concepts in optoelectronics”
M. Kneissl, M. Pristovsek
Lab Course in Advanced Experimental Physics
M. Kneissl, D. Bimberg, M. Dähne, C. Thomsen
40
Introduction to Physics for Engineering Students I + II
C. Thomsen
Introduction to Physics: Problems Solving for Graduate Students and Advanced
Diploma Students
C. Thomsen
Special Topics in Physics for Engineering Students
C. Thomsen
Special Topics in Semiconductor and Nanotube Research
C. Thomsen
External faculty members
Physics for Chemists and Food Chemists I + II
N. Esser, N. Nickel
Physics of Electronic Devices
R. Germer
Physics of Organs of Perception
R. Germer
Ultrasonics and Phonons
R. Germer
Organic Semiconductors
T. Kampen
Electrochemical Nanotechnology
H.-J. Lewerenz
Photovoltaic Solar Cells
H.-J. Lewerenz
Surface Physical Research on Energy Converted Semiconductor Structures
H.-J. Lewerenz
Basic principles of photovoltaic solar cells
N. Nickel
Hydrogen in Solid States
N. Nickel
Applied Surface Physic: Electron- and Photo-Optical Surface Analysis and Application
in Non-Linear Dynamic
H.-H. Rotermund, C. Punct
Neutrons as an Efficient Tool to Investigate Condensed Matter
K. Siemensmeyer, B. Lake
Neutron Scattering and Dynamics of Condensed Matter
K. Siemensmeyer, B. Lake
Advanced Magnetism
A. Tennant
Selective Sections of Neutron Scattering (Magnetism, Phase Transformations)
A. Tennant
41
Introduction to Physics for Engineering Students
C. Thomsen, H. Grahn
Introduction to X-ray- and Neutron Computed Tomography
W. Treimer
42
43
8.
PATENTS
Data transmission optoelectronic device
Europäische Patentanmeldung: AZ: 07 000 661.4 (13.01.2007)
US Patentanmeldung: AZ: 12/118.327 (09.05.2008)
Japanische Patentanmeldung Nr. 2008-162441 (18.08.2008)
Nicolai N. Ledentsov, Vitaly A. Shchukin, Dieter Bimberg
Verfahren und Anordnung zum Abtasten optischer Signale und zum Bilden
entsprechender Abtastwerte
Internationale Patentanmeldung Nr. PCT/DE2007/001662 (19.09.2007)
Holger Quast, Dieter Bimberg
Speicherzelle und Verfahren zum Speichern von Daten
Internationale Patentanmeldung Nr. PCT/DE2007/002182 (03.12.2007)
Martin Geller, Andreas Marent, Dieter Bimberg
Single-photon source and method for production and operation thereof
US Patentanmeldung: AZ: FIS-IP103 (03.07.2008)
Anatol Lochmann, Robert Seguin, Dieter Bimberg, Sven Rodt
Photonenpaarquelle und Verfahren zu deren Herstellung
Deutsche Patentanmeldung Nr. 10 2008 036 400.2-33 (01.08.2008)
Andrei Schliwa, Momme Winkelnkemper, Dieter Bimberg
44
45
9.
9.1
SCIENTIFIC ACTIVITIES
Department I
9.1.0 Staff
Secretary
Ulrike Grupe
Technical staff
Jörg Döhring
Ilona Gründler
Dipl.-Ing. Bernd Ludwig
Dipl.-Krist. Kathrin Schatke
Dipl.-Ing. Bernhard Tierock
Permanent guest scientists
Prof. Dr. Jürgen Christen
Priv.-Doz. Dr. Armin Dadgar
Prof. Dr. Gadi Eisenstein
Dr. Jungho Kim (until 31.07.2008)
Prof. Dr. Alois Krost
Prof. Dr. Nicolai N. Ledentsov
Dr. Vitali A. Shchukin
Principal scientists
Prof. Dr. Wolfgang Gehlhoff
Dr. Friedhelm Hopfer
Priv.-Doz. Dr. Udo Pohl
Dr. André Strittmatter
Senior scientists
Dr. Martin Geller (until 31.12.2007)
Dr. Matthias Kuntz (until 30.09.2007)
Dr. Matthias Lämmlin (until 31.03.2008)
Dr. Holger Quast (until 31.03.2007)
Dr. Sven Rodt
Dr. Andrei Schliwa
Dr. Robert Seguin (until 31.03.2008)
Dr. Momme Winkelnkemper
46
PhD candidates
Dipl.-Phys. Gerrit Fiol
Dipl.-Phys. Martin Geller (until 12.04.2007)
Dipl.-Phys. Tim Germann
Dipl.-Phys. Thorsten Kettler
Dipl.-Phys. Anatol Lochmann
Dipl.-Phys. Andreas Marent
Dipl.-Phys. Christian Meuer
Dipl.-Phys. Philip Moser
Dipl.-Phys. Alex Mutig
Dipl.-Phys. Tobias Nowozin
Dipl.-Phys. Irina Ostapenko
Dipl.-Phys. Kristijan Posilovic
Dipl.-Phys. Konstantin Pötschke
Dipl.-Phys. Andrei Schliwa (until 27.04.2007)
Dipl.-Phys. Oliver Schulz (until 05.06.2007)
Dipl.-Phys. Robert Seguin (until 28.01.2008)
Dipl.-Phys. Elisabeth Siebert (until 31.12.2008)
Dipl.-Phys. Erik Stock
Dipl.-Phys. Gernot Stracke
Dipl.-Phys. Mirko Stubenrauch
Dipl.-Phys. Waldemar Unrau
Dipl.-Phys. Till Warming
Dipl.-Phys. Momme Winkelnkemper (until 07.11.2008)
Diploma students
Dejan Arsenijevic
Max Feucker (until 30.09.2007)
Johannes Gelze
Tim Germann (until 11.02.2007)
Gerald Hönig
Sven Liebich (until 26.02.2008)
Gang Lou
Franziska Luckert (until 26.09.2008)
Philip Moser (until 17.07.2008)
Michael Christopher Münnix (until 16.06.2008)
Tobias Nowozin (until 09.05.2008)
Johannes Pohl (until 19.12.2008)
Holger Schmeckebier
Daniel Seidlitz
Elisabeth Siebert (until 01.07.2008)
Mirko Stubenrauch (until 03.07.2008)
Jan Amaru Töfflinger
Philip Wolf
Clemens Wündisch (until 11.01.2007)
47
9.1.1 Summary of activities
The activities of the department are grouped into five mutually connected research areas with
complementary objectives:
epitaxy of novel nano- and heterostructures,
physics of nanostructures,
nanophotonics,
high-frequency photonics, and
paramagnetic and cyclotron resonance.
The Center of Nanophotonics was expanded by the aquisistion of one of the finest electron
microscopes which is presently on the world market: the Zeiss Ultra 55. Now instantaneous
and precise control after each single processing-step is possible. Based on our own design our
workshop constructed a novel set-up for fabricating the oxide apertures of our VCSELs and
single/Entangled Photon Emitters – including in-situ control, another decisive step towards
better process control.
Addition of a sensor-system measuring the surface temperature of a wafer during MOCVDgrowth allows much more controlled and reproducible development of novel nanostructures
and wafers for devices based there-upon. The sensor-system was developed by our start-up
company LayTec GmbH, headed by Dr. Th. Zettler, which commemorated recently its
10th birthday. Improved homogenity across the wafer and run-to-run reproducibility presents a
permanent challenge and is decisive for rapid tests of novel device ideas, having limited
resources of researchers and consumables.
Acquisition of one of the most powerful bit pattern generators, the SHF 12100, and bit
error analyzers, the SHF 11100, was made possible by DFG, TUB and SHF, whose CEO,
Dr. F. Hieronymi, received his Ph.D. in 1994 at TUB for his research on high speed MSM
detectors.
The physics of formation of nanostructures at surfaces of varying orientations still presents
a major theoretical challenge. An important step towards a better understanding was obtained
by studying the time-evolution of the island-size distribution-function, using an approach
based on the Fokker-Planck equation. The competion between chemical potential drift and
thermal diffusion broadening of the island-size distribution results in Gaussian-like metastable
states. Fabrication of uniformly sized quantum-dot arrays with size selectivity can be achived
as a result of this study.
Optically pumped semiconductor disk lasers for wavelengths ranging from 950 to 1210 nm
were grown for the first time based on quantum dots and investigated in detail. Both, the
submonolayer (SML) growth-mode and the Stranski-Krastanow growth-mode were employed
for the active layers. An output-power of up to 1.4 W at continuous wave-operation was
achieved for InAs/GaAs-SML active layers emitting at 1040 nm. The results were obtained
within the European FP 6 “NATAL”-consortium and may lead to novel generations of disk
lasers.
The „New Scientist“ hailed results of our nanoflash research program as the potential “holy
grail” of future semiconductor nano-memories 106 years hole storage time were extrapolated
for GaSb/AlAs quantum dot memory structures. For GaSb/GaAs and InAs/GaAs quantum dot
structures write-times between 6 and 14 ns were demonstrated, being independent of the
storage time of the carriers.
Piezo-electric effects in both, InGaAs/GaAs and InGaN/GaN quantum dots, were in the
center of our research on electronics states of quantum dots in the past two years. The balance
of linear and quadratic parts of the piezo-electric fields was found to depend strongly on the
quantum dot’s shape and composition for the InGaAs/GaAs material system.
48
After deriving a consistent set of band-parameters for the group-III-nitrides, AlN, GaN and
InN, we use them as input for performing realistic eight-band k•p electronic structure
calculations for InGaN/GaN quantum dots. The polarization of excitonic recombination lines
from these quantum dots, as observed by us for the first time, could be consistently explained
by these calculations relating them to transistions connected with the A- or the B-valencebands in these wurtzite materials. Discovery and theoretical understanding of single q-bit
emission from InGaN quantum dots might well lead to the development of electrically-driven
single-photon emitters (q-bit emitters) at room temperature some day.
Such a q-bit emitter operating at low temperatures was demonstrated for single InAsquantum dots, inserted in an electrically driven LED, using an oxide aperture for current
confinement. To facilitate the future development of resonant cavity LEDs, using the Purcelleffect for enhancing emission intensity and modulation speed, a detailed study of exchange
interaction was performed. It showed that the fine-structure splitting is a function of QD size
and led to precise predictions, which size and composition of quantum dots are to be used in
the future for such devices.
Realization of complete temperature independence of the resonance transparency wavelength
in a planar multi-layer tilted-cavity wave-guide is decisive for future semiconductor lasers.
We discovered that temperature independence can be achieved, if the first derivative of the
refractive index with respect to temperature is positive and a non-linear function of the alloycomposition. Design predictions were derived and applied to the development of high-power
wavelength-stabilized tilted-cavity lasers emitting at 970 nm and showing side-mode
suppression ratios of more than 40 dB. The small-signal modulation band-width of these
devices was found at 3.5 GHz. S-parameter measurements indicate much higher frequencies
for more advanced processing and/or shorter cavity wavelength.
One-dimensional photonic-crystal lasers emitting in the 850 nm range were developed and
showed extremely high internal quantum efficiency of 93 % and a narrow vertical beam
divergence of 7.1°. Their brightness of 3 x 108 cm–2 /sr –1 is considered as being recordbreaking.
Ultra-high-speed edge-emitting lasers and amplifiers for future 100 Gbit Ethernet
systems stood in the center of other research. The ultra-low relative intensity noise observed
for InAs/GaAs quantum dot lasers was found to be correlated with the highly damped
modulation response we observered previously. This work, which was done in collaboraton
with Technion, Haifa, led to the bestowal of the Israeli Wolf-Prize for young scientists to
Amir Capua. The damping was explained and understood theoretically at the same time,
based on microscopic calculations of Coulomb scattering rates, describing Auger transistions
between quantum dots and the wetting layer. These investigations were performed in
collaboration with scientists of our Institute of Theoretical Physics.
Hybride and passive mode-locking of quantum-dot lasers, presently with repetition rates up
to 80 GHz, might present another essential device for the 100 G Ethernet. We discovered and
studied the possibility of obtaining sub-picosecond pulse-width and ultra-low timing jitter
below 200 fs.
Quantum-dot based amplifiers probed by our own mode-locked lasers for O-band optical
fibre applications, exhibited close-to-ideal noise figures of 4 dB and multi-wavelength
amplification according to CWDM standards. Pulse-broadening of a few hundred
femtoseconds only was observed for such amplifiers. Most recently cross-gain modulation at
40 GHz was demonstrated by us for QD-SOAs and theoretically modelled. This work was
done in the framework of the European FP 6-programs “TRIUMPH” and “SANDiE”, in
collaboration with our partners.
Optical interconnects for short distances, ranging from local area networks and computermemory to board-to-board interconnects, present another center of research of our group.
Our modelling shows that open-eyes beyond 20 Gbit/s operation with bit-error rates better
49
than 10-12 can be achieved up to very high temperatures. In fact, we recently reported such
operation of 980 nm-VCSELs up to 120 °C and observed operation up to 32 Gbit/s at 25 °C.
Still higher large signal modulation should be obtained using a novel patented concept, based
on VCSELs coupled to an electro-optical modulator, if this modulator is placed in the
resonant cavity. We have presently obtained 60 GHz electrical and about 35 GHz optical
bandwidth, limited by photo-detector response. The further development of these ideas will be
in the center of the work for the next years.
50
51
9.1.2 Books
Semiconductor Nanostructures
D. Bimberg (Ed.) Nanoscience and Technology,
Springer Verlag, Berlin, Heidelberg, 2008 (ISBN 978-3-540-77898-1)
9.1.3 Publications
The abstracts of papers marked by* are reprinted in section 9.1.7
a)
Novel Nano- and Heterostructures
1.*
Epitaxy of multimodal InAs/GaAs quantum dot ensembles
K. Pötschke, U.W. Pohl , D. Feise, and D. Bimberg
Proc. of ICMOVPE-XIII, Miyazaki, Japan, May 2006, Special issue of Journal of
Crystal Growth (K. Onabe, A. Usui, and N. Kobayashi, Eds.) 298, 567 (2007)
2.
InAs/InP quantum dots (QD): From fundamental understanding to coupled QD
1.55 µm laser applications
C. Cornet, M. Hayne, A. Schliwa, F. Doré, J. Even, D. Bimberg, V.V. Moshchalkov,
and S. Loualiche
Phys. Stat. Sol. (c) 4 (2), 458 (2007)
3.
MBE-grown metamorphic lasers for applications at telecom wavelengths
N.N. Ledentsov, V.A. Shchukin, T. Kettler, K. Posilovic, D. Bimberg, L.Ya.
Karachinsky, A.Yu. Gladyshev, M.V. Maximov, I.I. Novikov, Yu.M. Shernyakov,
A.E. Zhukov, V.M. Ustinov, A.R. Kovsh
Proc. of MBE-14, Tokyo, Japan, September 2006, Special issue of Journal of Crystal
Growth (J. Yoshino, H. Akinaga, and H. Asahi, Eds.) 301-2, 914 (2007)
4.
MBE-grown ultra-large aperture single mode single-wavelength vertical-cavity
surface-emitting laser with all-epitaxial filter section
S. Blokhin, L. Karachinsky, I. Novikov, S. Kuznetsov, Yu. Shernyakov, M. Maximov,
A. Mutig, F. Hopfer, A. Kovsh, S. Mikhrin, I. Krestnikov, D. Livshits, V. Ustinov,
N. Ledentsov, and D. Bimberg
Proc. of MBE-14, Tokyo, Japan, September 2006, Special issue of Journal of Crystal
Growth (J. Yoshino, H. Akinaga, and H. Asahi, Eds.) 301-2, 945 (2007)
5.
Merging nanoepitaxy and nanophotonics
N.N. Ledentsov, V.A. Shchukin, D. Bimberg
Future Trends in Microelectronics, Up to the Nanocreek (S. Luryi, J. Xu, A.Zaslavsky,
Eds.), pp. 401 (2007)
6.*
Metastable states of surface nanostructure arrays studied using a Fokker-Planck
equation
T.P. Munt, D.E. Jesson, V.A. Shchukin, and D. Bimberg
Physical Review B 75, 85422 (2007)
7.
MOCVD of InGaAs/GaAs quantum dots for lasers emitting close to 1.3 µm
T.D. Germann, A. Strittmatter, T. Kettler, K. Posilovic, U.W. Pohl, and D. Bimberg
Proc. of ICMOVPE-XIII, Miyazaki, Japan, May 2006, Special issue of Journal of
Crystal Growth (K. Onabe, A. Usui, and N. Kobayashi, Eds.) 298, 591 (2007)
52
8.
Recombination characteristics of the proton and neutron irradiated semiinsulating GaN structures
E. Gaubas, J. Vaitkus, K. Kazlauskas, A. Žukauskas, J. Grant, R. Bates, V. O'shea,
A. Strittmatter, D. Bimberg, and P. Gibart
Proc. of RESMDD-6, Florence, Italy, October 2006, Nuclear Instruments and Methods
in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated
Equipment 583 (1), 181 (2007)
9.
Submonolayer quantum dots for high speed surface emitting lasers
N.N. Ledentsov, D. Bimberg, F. Hopfer, A. Mutig, V.A. Shchukin, A.V. Savel’ev,
G. Fiol, E. Stock, H. Eisele, M. Dähne, D. Gerthsen, U. Fischer, D. Litvinov,
A. Rosenauer, S.S. Mikhrin, A.R. Kovsh, N.D. Zakharov, and P. Werner
Nanoscale Research Letters 2, 417 (2007)
10.
1040 nm vertical external cavity surface emitting laser based on InGaAs quantum
dots grown in Stranski-Krastanow regime
A. Strittmatter, T.D. Germann, J. Pohl, U.W. Pohl, D. Bimberg, J. Rautiainen,
M. Guina, and O.G. Okhotnikov
Electr. Lett. 44 (4), 290 (2008)
11.
Effect of excitation level on the optical properties of GaAs/AlGaO microdisks with
an active region containing InAs quantum dots
A.M. Nadtochiy, S.A. Blokhin, A.V. Sakharov, M.M. Kulagina, Y.M. Zadiranov,
N.Y. Gordeev, M.V. Maksimov, V.M. Ustinov, N.N. Ledentsov, E. Stock, T. Warming,
and D. Bimberg
Semiconductors 42 (10), 1228 (2008)
12.
InAs/GaAs quantum qots with multimodal size distribution
U.W. Pohl
Chapter 3 in “Self-assembled quantum dots” (Z. M. Wang, Ed.) pp. 43 – 66,
Springer, New York (2008)
13.* Progress in epitaxial growth and performance of quantum dot and quantum wire
lasers
N.N. Ledentsov, D. Bimberg, and Z.I. Alferov
Journal of Lightwave Technology 26 (9-12), 1540 (2008)
14.* Quantum-dot semiconductor disk lasers
T.D. Germann, A. Strittmatter, U.W. Pohl, D. Bimberg, J. Rautiainen, M. Guina,
O.G. Okhotnikov
Proc. of ICMOVPE-XIV, Metz, France, June 2008, Special issue of Journal of Crystal
Growth (F. Scholz, S. Irvine, and B. Mullin, Eds.) 310 (23), 5182 (2008)
15.
Structural investigation of InAs /GaAs dots-in-a-well nanostructures
A. Lenz, H. Eisele, R. Timm, L. Ivanova, H.-Y. Liu, M. Hopkinson, U. W. Pohl,
M. Dähne
Physica E 40, 1988 (2008)
53
16.
Suppression of the wavelength blue shift during overgrowth of InGaAs-based
quantum dots
A. Strittmatter, T.D. Germann, T. Kettler, K. Posilovic, J. Pohl, U.W. Pohl,
and D. Bimberg
Proc. of ICMOVPE-XIV, Metz, France, June 2008, Special issue of Journal of Crystal
Growth (F. Scholz, S. Irvine, and B. Mullin, Eds.) 310 (23), 5066 (2008)
17.
Temperature-stable operation of a quantum dot semiconductor disk laser
T.D. Germann, A. Strittmatter, J. Pohl, U.W. Pohl, D. Bimberg, J. Rautiainen,
Appl. Phys. Lett. 93, 51104 (2008)
b)
Physics of Nanostructures
18.* 106 years extrapolated hole storage time in GaSb/AlAs quantum dots
A. Marent, M. Geller, A. Schliwa, D. Feise, K. Pötschke, D. Bimberg, N. Akçay,
and N. Öncan
Appl. Phys. Lett. 91, 242109 (2007)
19.
Complete ground state gain recovery after ultrashort double pulses in quantum
dot based semiconductor optical amplifier
S. Dommers, V.V. Temnov, U. Woggon, J. Gomis, J. Martinez-Pastor, M. Lämmlin,
D. Bimberg
Appl. Phys. Lett. 90, 33508 (2007)
20.
Dependence of the band-gap pressure coefficients of self-assembled InAs/GaAs
quantum dots on the quantum dot size
C. Kristukat, A.R. Goñi, K. Pötschke, D. Bimberg, and C. Thomsen
Phys. Stat. Sol. (b) 244 (1), 53 (2007)
21.
Determination of quantum dot morphology from magnetooptical properties
V. Křapek, A. Schliwa, and D. Bimberg
Acta Physica Polonica A 112 (2), 339 (2007)
22.
Direct observation of charge-carrier capture in an array of self-assembled
InAs/GaAs quantum dots
V.I. Zubkov, I.S. Shulgunova, A.V. Solomonov, M. Geller, A. Marent, D. Bimberg,
A.E. Zhukov, E.S. Semenova, and V.M. Ustinov
Bulletin of the Russian Academy of Sciences: Physics 71 (1), 106 (2007)
23.* Impact of size, shape, and composition on piezoelectric effects and electronic
properties of In(Ga)As/GaAs quantum dots
A. Schliwa, M. Winkelnkemper, and D. Bimberg
24.
Magnetooptical properties of quantum dots: Influence of the piezoelectric field
V. Křápek, A. Schliwa, and D. Bimberg
Proc. of EP2DS-17, Genova, Italy, July 2007, Special issue of Physica E:
Low-Dimensional Systems & Nanostructures (G. Goldoni and L. Sorba, Eds.) 40 (5),
1163 (2007)
54
25.
Nanostructures for nanoelectronics:
No potential for room temperature applications ?
M. Geller, F. Hopfer, D. Bimberg
Proc. of LDSD 2007, San Andres, Columbia, April 2007, Special issue of
Microelectronics Journal (M. Henini, I. Hernández-Calderón, Eds.) 39 (3-4), 302 (2007)
26.* Polarized emission lines from A- and B-type excitonic complexes in single
InGaN/GaN quantum dots
M. Winkelnkemper, R. Seguin, S. Rodt, A. Schliwa, L. Reissmann, A. Strittmatter,
A. Hoffmann, D. Bimberg
J. Appl. Phys. 101, 113708 (2007)
27.
Relaxation dynamics of bimodally distributed CdSe quantum dots
P. Bajracharya, T.A. Nguyen, S. Mackowski, L.M. Smith, H.P. Wagner, U.W. Pohl,
D. Bimberg, M. Strassburg
28.
Semianalytical evaluation of linear and nonlinear piezoelectric potentials for
quantum nanostructures with axial symmetry
J. Even, F. Dore, C. Cornet, L. Pedesseau, A. Schliwa, and D. Bimberg
Appl. Phys. Lett. 91, 122112 (2007)
29.
Size-dependent binding energies and fine-structure splitting of excitonic complexes
in single InAs/GaAs quantum dots
S. Rodt, R. Seguin, A. Schliwa, F. Guffarth, K. Pötschke, U.W. Pohl, D. Bimberg
J. of Luminescence 122, 735 (2007)
30.
Theoretical study of electronic and optical properties of inverted GaAs/AlxGa1-xAs
quantum dots with smoothed interfaces in an external magnetic field
V. Mlinar, A. Schliwa, D. Bimberg, and F.M. Peeters
31.
Towards a universal memory based on self-organized quantum dots
A. Marent, M. Geller, D. Feise, K. Pötschke, and D. Bimberg
Proc. of MSS-13, Genova, Italy, July 2007, Special issue of Physica E:
Low-Dimensional Systems & Nanostructures (G. Goldoni and L. Sorba, Eds.) 40 (6),
1811 (2007)
32.* A write time of 6 ns for quantum dot–based memory structures
M. Geller, A. Marent, T. Nowozin, D. Bimberg, N. Akçay, and N. Öncan
Appl. Phys. Lett. 92, 92108 (2008)
33.* Consistent set of band parameters for the group-III nitrides AlN, GaN, and InN
P. Rinke, M. Winkelnkemper, A. Qteish, D. Bimberg, J. Neugebauer, and M. Scheffler
34.* Decay dynamics of neutral and charged excitonic complexes in single InAs/GaAs
quantum dots
M. Feucker, R. Seguin, S. Rodt, A. Hoffmann, and D. Bimberg
Appl. Phys. Lett. 92, 63116 (2008)
55
35.
Excitonic Mott transition in type-II quantum dots
B. Bansal, M. Hayne, M. Geller, D. Bimberg, V.V. Moshchalkov
36.
From k•p to atomic calculations applied to semiconductor heterostructures
L. Pedesseau, C. Cornet, F. Doré, J. Even, A. Schliwa, and D. Bimberg
Journal of Physics.: Conf. Ser. 107, 12009 (2008)
37.* GaN/AlN quantum dots for single qubit emitters
M. Winkelnkemper, R. Seguin, S. Rodt, A. Hoffmann, and D. Bimberg
Journal of Physics: Condensed Matter 20, 454211 (2008)
38.* Impact of Coulomb scattering on the ultrafast gain recovery in InGaAs quantum
dots
J. Gomis-Bresco, S. Dommers, V.V. Temnov, and U. Woggon, M. Laemmlin,
D. Bimberg, E. Malić, M. Richter, E. Schöll, and A. Knorr
Physical Review Letters 101, 256803 (2008)
39.
InGaAs quantum dot population and polarisation dynamics for ultrafast pulse
train amplification
J. Gomis-Bresco, S. Dommers, V. Temnov, U. Woggon, M. Laemmlin, D. Bimberg,
E. Malić, M. Richter, E. Schöll, A. Knorr
IEEE Proc. of CLEO/QELSC, San Jose, USA, May 2008, Vol. 1-9, 3599 (2008)
40.
Model of Raman scattering in self-assembled InAs/GaAs quantum dots
S.N. Klimin, V.M. Fomin, J.T. Devreese, and D. Bimberg
41.* Onion-like growth and inverted many-particle energies in quantum dots
D. Bimberg
Applied Surface Science 255, 799 (2008)
42.
Origin of the broad lifetime distribution of localized excitons in InGaN/GaN
quantum dots
M. Winkelnkemper, M. Dworzak, T.P. Bartel, A. Strittmatter, A. Hoffmann,
and D. Bimberg
Phys. Stat. Sol. (b) 245 (12), 2766 (2008)
43.
Polarized emission lines from single InGaN/GaN quantum dots:
Role of the valence band structure of Wurtzite group-III nitrides
M. Winkelnkemper, R. Seguin, S. Rodt, A. Schliwa, L. Reissmann, A. Strittmatter,
Proc. of MSS-13, Genova, Italy, July 2007, Special issue of Physica E: LowDimensional Systems & Nanostructures (G. Goldoni and L. Sorba, Eds.) 40 (6), 2217
(2008)
44.
Self-organized quantum dots for future semiconductor memories
M. Geller, A. Marent, T. Nowozin, and D. Bimberg
Journal of Physics: Condensed Matter 20, 454202 (2008)
45.* Size-tunable exchange interaction in InAs/GaAs quantum dots
U.W. Pohl, A. Schliwa, R. Seguin, S. Rodt, K. Pötschke, D. Bimberg
Adv. in Sol. State Phys. (R. Haug, Ed.) 46, 45 (2008)
56
46.
A novel nonvolatile memory based on self-organized quantum dots
A. Marent, M. Geller, D. Bimberg
Microelectronics Journal , in press (2009)
c)
Nanophotonics
47.
A high-power 975 nm tilted cavity laser with a 0.13 nm K-1 thermal shift of the
lasing wavelength
V.A. Shchukin, N.N. Ledentsov, L.Ya. Karachinsky, I.I. Novikov, Yu.M. Shernyakov,
N.Yu. Gordeev, M.V. Maximov, M.B. Lifshits, A.V. Savelyev, A.R. Kovsh,
I.L. Krestnikov, S.S. Mikhrin, and D. Bimberg
Semiconductor Science and Technology 22, 1061 (2007)
48.* Electrically driven quantum dot single photon source
A. Lochmann, E. Stock, O. Schulz, F. Hopfer, D. Bimberg, V.A. Haisler, A.I. Toropov,
A.K. Bakarov, M. Scholz, S. Büttner, and O. Benson
Phys. Stat. Sol. (c) 4 (2), 547 (2007)
49.* High-power wavelength stabilized 970 nm tilted cavity laser with a 41.3 dB side
mode suppression ratio
L.Ya. Karachinsky, M. Kuntz, G. Fiol, V.A. Shchukin, N.N. Ledentsov, D. Bimberg,
A.R. Kovsh, S.S. Mikhrin, I.I. Novikov, Yu.M. Shernyakov, M.V. Maximov
Appl. Phys. Lett. 91, 241112 (2007)
50.
Non-classical light emission from a single electrically driven quantum dot
M. Scholz, S. Buttner, O. Benson, A.I. Toropov, A.K. Bakarov, A.K. Kalagin,
A. Lochmann, E. Stock, O. Schulz, F. Hopfer, V.A. Haisler, and D. Bimberg
Optics Express 15 (15), 9107 (2007)
51.* Resonance wavelength in planar multilayer waveguides:
Control and complete suppression of temperature sensitivity
M.B. Lifshits, V.A. Shchukin, N.N. Ledentsov, and D. Bimberg
Semicond. Sci. and Technology 22, 380 (2007)
52.
Special issue on Optoelectronic Devices based on Quantum Dots
P. Bhattacharya, D. Bimberg, and Y. Arakawa
Proc. of the IEEE, Special Issue: Optoelectronic Devices Based on Quantum Dots
(R.J. Trew, J.E. Brittain, Eds.) 95 (9), 1718 (2007)
53.
The impact of thermal effects on emission characteristics of asymmetrical AlGaOwaveguide microdisks based on quantum dots
S.A. Blokhin, A.V. Sakharov, A.M. Nadtochy, M.M. Kulagina, Yu.M. Zadiranov,
N.Yu. Gordeev, M.V. Maximov, V.M. Ustinov, N.N. Ledentsov, E. Stock, T. Warming,
and D. Bimberg
Appl. Phys. Lett. 91, 121108 (2007)
54.
Characterisation of an InAs quantum dot semiconductor disk laser
P. Schlosser, S. Calvez, J.E. Hastie, S. Jin, T.D. Germann, A. Strittmatter, U.W. Pohl,
D. Bimberg, and M.D. Dawson
57
55.
High brightness and ultra-narrow beam 850 nm GaAs/AlGaAs photonic band
crystal lasers and first uncoupled PBC single-mode arrays
T. Kettler, K. Posilovic, J. Fricke, P. Ressel, A. Ginolas, U.W. Pohl, V.A. Shchukin,
N.N. Ledentsov, D. Bimberg, J. Jönsson, M. Weyers, G. Erbert, and G. Tränkle
IEEE Proc. of ISLC, Sorrento, Italy, September 2008, CFP08SLC-CDR, ThC6 (2008)
56.* High-power low-beam divergence edge-emitting semiconductor lasers with 1- and
2-D photonic bandgap crystal waveguide
M.V. Maximov, Y.M. Shernyakov, I.I. Novikov, N.Yu. Gordeev,L.Ya. Karachinsky,
U. Ben-Ami, D. Bortman-Arbiv, A. Sharon, V.A. Shchukin, N.N. Ledentsov, T. Kettler,
K. Posilovic, and D. Bimberg
IEEE Journal of Selected Topics in Quantum Electronics 14 (4), 1113 (2008)
57.
High-power one-, two-, and three-dimensional photonic crystal edge-emitting
laser diodes for ultrahigh brightness applications
N.Yu. Gordeev, M.V. Maximov, Y.M. Shernyakov, I.I. Novikov, L.Ya. Karachinsky,
V.A. Shchukin, T. Kettler, K. Posilovic, N.N. Ledentsov, D. Bimberg, R. Duboc,
A. Sharon, D.B. Arbiv, U. Ben-Ami
Proc. of OPTO 2008 at Photonics West, San Jose, USA, January 2008, SPIE: Physics
and Simulation of Optoelectronic Devices XVI (M. Osinski, F. Henneberger,
K. Edamatsu, Eds.) 6889, OW-1 (2008)
58.
High-power semiconductor disk laser based on InAs/GaAs submonolayer
quantum dots
T.D. Germann, A. Strittmatter, J. Pohl, U.W. Pohl, D. Bimberg, J. Rautiainen,
Appl. Phys. Lett. 92, 101123 (2008)
59.
Improved optical confinement 1.55 µm InAs/GaInAsP quantum dot lasers
grown by MOVPE
D. Franke, P. Harde, J. Kreissl, M. Moehrle, W. Rehbein, H. Kuenzel, U.W. Pohl,
and D. Bimberg
IEEE Proc. of IPRM-20, Versailles, France, May 2008, CFP08IIP-CDR, (2008)
60.* Quantum dot based nanophotonics and nanoelectronics
D. Bimberg
Electr. Lett. 44 (3), 168 (2008)
61.
Single-lobe single-wavelength lasing in ultrabroad-area vertical-cavity
surface-emitting lasers based on the integrated filter concept
S.A. Blokhin, L.Y. Karachinsky, I.I. Novikov, N.Y. Gordeev, A.V. Sakharov,
N.A. Maleev, A.G. Kuzmenkov, Y.M. Shernyakov, M.V. Maximov, A.R. Kovsh,
S.S. Mikhrin, V.A. Shchukin, N.N. Ledentsov, V.M. Ustinov, and D. Bimberg
IEEE Journal of Quantum Electronics 44 (8), 724 (2008)
62.
Tilted cavity concept for the high-power wavelength stabilized diode lasers
L.Ya. Karachinsky, I.I. Novikov, G. Fiol, M. Kuntz, Yu.M. Shernyakov,
N.Yu. Gordeev, M.V. Maximov, M.B. Lifshits, T. Kettler, K. Posilovic, V.A. Shchukin,
N.N. Ledentsov, S.S. Mikhrin, D. Bimberg
Proc. of SPIE: 6th Int. Conf. on Photonics, Devices, and Systems IV, Prague, August
2008 (P. Tománek, D. Senderáková, M. Hrabovský, Eds.) 7138, 713804 (2008)
58
63.* Ultrahigh-brightness 850 nm GaAs/AlGaAs photonic crystal laser diodes
K. Posilovic, T. Kettler, V.A. Shchukin, N.N. Ledentsov, U.W. Pohl, D. Bimberg,
J. Fricke, A. Ginolas, G. Erbert, G. Tränkle, J. Jönsson, and M. Weyers
Appl. Phys. Lett. 93, 221102 (2008)
d)
High Frequency Photonics
64.
20 Gb/s 85 °C error-free operation of VCSELs based on submonolayer deposition
of quantum dots
F. Hopfer, A. Mutig, G. Fiol, M. Kuntz, V.A. Shchukin, V.A. Haisler, T. Warming,
E. Stock, S.S. Mikhrin, I.L. Krestnikov, D.A. Livshits, A.R. Kovsh, C. Bornholdt,
A. Lenz, H. Eisele, M. Dähne, N.N. Ledentsov, and D. Bimberg
65.* Coulomb damped relaxation oscillations in semiconductor quantum dot lasers
E. Malić, M.J.P. Bormann, P. Hövel, M. Kuntz, D. Bimberg, A. Knorr, and E. Schöll
66.* Direct correlation between a highly damped modulation response and ultra low
relative intensity noise in an InAs/GaAs quantum dot laser
A. Capua, L. Rozenfeld, V. Mikhelashvili, G. Eisenstein, M. Kuntz, M. Laemmlin,
and D. Bimberg
Optics Express 15 (9), 5388 (2007)
67.
High frequency nanophotonic devices
D. Bimberg, G. Fiol, C. Meuer, M. Laemmlin, and M. Kuntz
Proc. of Photonics West, San José, USA, January 2007, SPIE: Novel In-Plane
Semiconductor Lasers VI (C. Mermelstein, D.P. Bour, Eds.) 6485, 64850X (2007)
68.* High speed quantum dot vertical cavity surface emitting lasers
N.N. Ledentsov, F. Hopfer, and D. Bimberg
69.* High-speed mode-locked quantum-dot lasers and optical amplifiers
M. Kuntz, G. Fiol, M. Laemmlin, C. Meuer, and D. Bimberg
70.
Novel concepts for ultrahigh-speed quantum-dot VCSELs and edge-emitters
N.N. Ledentsov, F. Hopfer, A. Mutig, V.A. Shchukin, A.V. Savel’ev, G. Fiol,
M. Kuntz, V.A. Haisler, T. Warming, E. Stock, S.S. Mikhrin, A.R. Kovsh,
C. Bornholdt, A. Lenz, H. Eisele, M. Dähne, N.D. Zakharov, P. Werner,
and D. Bimberg
Proc. of OPTO 2007 at Photonics West, San José, USA, January 2007,
SPIE: Physics and simulation of optoelectronic devices XV,
(M. Osinski,F. Henneberger, Y. Arakawa, Eds.) 6468, 646810 (2007)
71.
Stability of the mode-locked regime in quantum dot lasers
E.A. Viktorov, P. Mandel, M. Kuntz, G. Fiol, D. Bimberg, A.G. Vladimirov,
and M. Wolfrum
Appl. Phys. Lett. 91, 231116 (2007)
59
72.
120 °C 20 Gbit/s Operation of 980 nm Single Mode VCSEL
A. Mutig, G. Fiol, P. Moser, F. Hopfer, M. Kuntz V.A. Shchukin, N.N. Ledentsov,
D. Bimberg, S.S. Mikhrin, I.L. Krestnikov, D.A. Livshits, and A.R. Kovsh
IEEE Proc. of ISLC, Sorrento, Italy, September 2008, CFP08SLC-CDR, MB2 (2008)
73.* 120 °C 20 Gbit/s operation of 980 nm VCSEL
A. Mutig, G. Fiol, P. Moser, D. Arsenijevic, V.A. Shchukin, N.N. Ledentsov,
S.S. Mikhrin, I.L. Krestnikov, D.A. Livshits, A.R. Kovsh, F. Hopfer, and D. Bimberg
Electr. Lett. 44 (22), 1305 (2008)
74.* 40 GHz small-signal cross-gain modulation in 1.3 µm quantum dot semiconductor
optical amplifiers
C. Meuer, J. Kim, M. Laemmlin, S. Liebich, D. Bimberg, A. Capua, G. Eisenstein,
R. Bonk, T. Vallaitis, J. Leuthold, A.R. Kovsh, and I.L. Krestnikov
Appl. Phys. Lett. 93, 51110 (2008)
75.
A wavelength conversion scheme based on a quantum-dot semiconductor optical
amplifier and a delay interferometer
S. Sygletos, R. Bonk, P. Vorreau, T. Vallaitis, J. Wang, W. Freude, J. Leuthold,
C. Meuer, D. Bimberg, R. Brenot, F. Lelarge, G. H. Duan
IEEE Proc. of ICTON, Athens, Greece, June 2008, Vol. 2, 149 (2008)
76.
An interferometric configuration for performing cross-gain modulation with
improved signal quality
R. Bonk, P. Vorreau, S. Sygletos, T. Vallaitis, J. Wang, W. Freude, J. Leuthold,
R. Brenot, F. Lelarge, G.H. Duan, C. Meuer, S. Liebich, M. Laemmlin, D. Bimberg
Proc. of OFC/NFOEC 2008, San Diego, USA, February 2008 (Optical Society of
America), JWA70 (2008)
77.
Decoupled electron and hole dynamics in the turn-on behavior of quantum-dot
lasers
K. Lüdge, E. Malić, M. Kuntz, D. Bimberg, E. Schöll
IEEE Proc. of ISLC, Sorrento, Italy, September 2008, CFP08SLC-CDR, MC4 (2008)
78.
Dynamic response of quantum dot lasers – Influence of nonlinear electron-electron
scattering
K. Lüdge, E. Malić, M. Kuntz, D. Bimberg, A. Knorr, E. Schöll
79.
Enhancing small-signal cross-gain modulation of quantum-dot optical amplifiers
by injecting carriers to excited states
J. Kim, M. Laemmlin, C. Meuer, S. Liebich, D. Bimberg, and G. Eisenstein
Proc. of OFC/NFOEC 2008, San Diego, USA, February 2008 (Optical Society of
America), OTuC3 (2008)
80.
High speed cross gain modulation using quantum dot semiconductor optical
amplifiers at 1.3 µm
C. Meuer, M. Laemmlin, S. Liebich, J. Kim, D. Bimberg, A. Capua, G. Eisenstein,
R. Bonk, T. Vallaitis, and J. Leuthold
60
81.
High-speed directly and indirectly modulated VCSELs
F. Hopfer, A. Mutig, A. Strittmatter, G. Fiol, P. Moser, D. Bimberg, V.A. Shchukin,
N.N. Ledentsov, J.A. Lott, H. Quast, M. Kuntz, S.S. Mikhrin, I.L. Krestnikov,
D.A. Livshits, A.R. Kovsh, C. Bornholdt
IEEE Proc. of IPRM-20, Versailles, France, May 2008, CFP08IIP-CDR (2008)
82.
Multi-wavelength all-optical regeneration
I. Tomkos, J. Leuthold, P. Petropoulos, D. Bimberg, A. Ellis
Digest of the LEOS Summer Topical Meeting , Acapulco, Mexico, July 2008, p. 167
(2008)
83.
Nonlinear properties of quantum dot semiconductor optical amplifiers at 1.3 µm
D. Bimberg, C. Meuer, M. Laemmlin, S. Liebich, J. Kim, A. Kovsh, I. Krestnikov,
G. Eisenstein
Chinese Optics Letters 6 (10), 724 (2008)
84.
Quantum dot photonics: Edge emitter, amplifier and VCSEL
F. Hopfer, M. Kuntz, M. Lämmlin, G. Fiol, N.N. Ledentsov, A.R. Kovsh, S.S. Mikrin,
I. Kaiander, V. Haisler, A. Lochmann, A. Mutig, C. Schubert, A. Umbach,
V.M. Ustinov, U.W. Pohl, and D. Bimberg
Proc. of SPIE: CAOL 2005, Yalta, Ukraine, September 2005, Photonics Active Devices
(I.A. Sukhoivanov, V.A. Svich, Y.S. Shmaliy, Eds.) 7009, 700902 (2008)
85.
Quantum dot semiconductor optical amplifiers for wavelength conversion using
cross-gain modulation
D. Bimberg, C. Meuer, M. Laemmlin, S. Liebich, J. Kim, G. Eisenstein,
and A. R. Kovsh
IEEE Proc. of ICTON, Athens, Greece, 2008, Vol. 2, 141 (2008)
86.
Semiconductor quantum dots
D. Bimberg
Chapter 2 in ‘Optical Fiber Telecommunications V A: Components and Subsystems’
(I. Kaminow, T. Li, A. Willner, Eds.), p. 23, Academic Press, Elsevier (2008)
87.
Slow and fast gain and phase dynamics in a quantum dot semiconductor optical
amplifier
T. Vallaitis, C. Koos, R. Bonk, W. Freude, M. Lämmlin, C. Meuer, D. Bimberg,
J. Leuthold
Optics Express 16 (1), 170 (2008)
88.* Static gain saturation in quantum dot semiconductor optical amplifiers
C. Meuer, J. Kim, M. Laemmlin, S. Liebich, A. Capua, G. Eisenstein, A.R. Kovsh,
S.S. Mikhrin, I.L. Krestnikov, and D. Bimberg
Optics Express 16 (11), 8269 (2008)
89.
Static gain saturation model of quantum-dot semiconductor optical amplifiers
J. Kim, M. Laemmlin, C. Meuer, D. Bimberg, and G. Eisenstein
IEEE Journal of Quantum Electronics 44 (7), 658 (2008)
61
90.
Turn-on dynamics and modulation response in semiconductor quantum dot lasers
K. Lüdge, M.J.P. Bormann, E. Malić, P. Hövel, M. Kuntz, D. Bimberg, A. Knorr,
and E. Schöll
Physical Review B 78 (3), 35316 (2008)
91.* Ultrahigh–speed electrooptically–modulated VCSELs: Modeling and experimental
results
V.A. Shchukin, N.N. Ledentsov, J.A. Lott, H. Quast, F. Hopfer, L.Ya. Karachinsky,
M. Kuntz, P. Moser, A. Mutig, A. Strittmatter, V.P. Kalosha, and D. Bimberg
Proc. of OPTO 2008 at Photonics West, San Jose, USA, January 2008, SPIE: Physics
and Simulation of Optoelectronic Devices XVI (M. Osinski, F. Henneberger,
K. Edamatsu, Eds.) 6889, OH-1 (2008)
e)
Magnetic Resonance Investigations
92.
Electron paramagnetic resonance characterization of Mn- and Co-doped ZnO
nanowires
A. Ankiewicz, W. Gehlhoff, A. Rahm, M. Lorenz, M. Grundmann, M.C. Carmo,
and N.A. Sobolev
AIP Conf. Proceedings Vol. 893, 63 (2007)
93.
Electron paramagnetic resonance characterization in TM-doped ZnO nanowires
A. Ankiewicz, W. Gehlhoff, E. M. Kaidashev, A. Rahm, M. Lorenz, M. Grundmann
M.C. Carmo, and N.A. Sobolev
J. Appl. Phys. 101, 024324 (2007)
94.
Local order in ZnGeP2:Mn crystals
R. Bacewicz, A. Pitnoczka, W. Gehlhoff, V. G. Voevodin
Phys. Stat. Sol. (a) 204, 2296 (2007)
95.
Spin interference in silicon one-dimensional rings
N.T. Bagraev, N.G. Galkin, W. Gehlhoff, L.E. Klyachkin, A.M. Malyarenko,
and I.A. Shelykh
AIP Conf. Proceedings Vol. 893, 693 (2007)
96.
ODMR of impurity centers embedded in silicon microcavities
V.A. Maskov, V.V. Romanov, T.N. Shelykh
Physica E 40, 1627 (2008)
97.* Phase and amplitude response of ‘0.7 feature’ caused by holes in silicon onedimensional wires and rings
N.T. Bagraev, N.G. Galkin, W. Gehlhoff, L.E. Klyachkin, and A.M. Malyarenko
J. Phys.: Condens. Matter 20, 164202 (2008)
98.
Spin-dependent transport of holes in quantum wells confined by superconductor
barriers
N.T. Bagraev, W. Gehlhoff, L.E. Klyachkin, A.A. Kudravtsev, A.M. Malyarenko,
G.A. Oganesyan, D.S. Polskin, V.V. Romanov
Physica C 468, 840 (2008)
62
99.
Spin interference of holes in silicon one-dimensional rings
I.A. Shelykh,
Physica E 40, 1338 (2008)
100.* Surface modification of Co-doped ZnO nanocrystals and its effects on the
magnetic properties
A.S Pereira, A.O. Ankiewicz, W. Gehlhoff, A. Hoffmann, S. Pereira, T. Trindade,
M. Grundmann, M.C. Carmo, and N.A. Sobolev
Journal of Applied Physics 103, 07D140 (2008).
101. Magnetic and structural properties of transition metal doped zinc-oxide
nanostructures
A.O. Ankiewicz, W. Gehlhoff, J.S. Martins, A.S. Pereira, S. Pereira, A. Hoffmann,
E.M. Kaidashev, A. Rahm, M. Lorenz, M. Grundmann, M.C. Carmo, T. Trindade,
and N.A. Sobolev
Phys. Stat. Sol. (b) accepted (2009)
63
9.1.4 Invited talks
D. Bimberg
High frequency nanophotonic devices
Photonics West,
San José, California, USA, January 2007
D. Bimberg
Colloquium at University of California,
Berkeley, USA, January 2007
D. Bimberg
Quantum dot lasers & new device concepts
for high-brightness applications
Workshop at the World Photonics Congress and Laser 2007 Fair,
Munich, Germany, June 2007
D. Bimberg
15th Int. Symp. "Nanostructures: Physics and Technology",
Novosibirsk, Russia, June 2007
D. Bimberg
Quantum dots: Genesis, the excitonic zoo, and its applications
Int. Nano-Optoelectronic Workshop (INOW 2007),
Beijing, China, July/August 2007
D. Bimberg
Onion-like growth and inverted many-particle energies
in quantum dots
11th Int. Conf. on the Formation of Semiconductor Interfaces,
Manaus, Brazil, August 2007
D. Bimberg
Quantum dots: Genesis, the excitonic zoo, and its applications
Symposium on Vacuum based Science and Technology,
Greifswald, Germany, September 2007
D. Bimberg
Merging VCSELs and nanostructures
for future ultrafast data communication
Int. Symp. on VCSEL and Integrated Photonics,
Tokyo, Japan, December 2007
D. Bimberg
Nanophotonics and -electronics: Joint research
for future communication and information systems
Russian-German Workshop on Nanotechnology:
"New Prospects for Co-operation in Nanotechnologies",
Moscow, Russia, December 2007
D. Bimberg
Quantenpunkte: Genesis, der exzitonische Zoo,
fliegende q-bits und nanoflash Speicher
First Scientific Symposium of the Graduate School BuildMoNa,
Leipzig, Germany, February 2008
64
D. Bimberg
Small is beautiful: Nanos for photonics and medicine
Netzwerktagung für Stipendiaten der Alexander von HumboldtStiftung, Berlin, Germany, April 2008
D. Bimberg
Quantum structures for quantum communication
and quantum memories
St. Petersburg Scientific Forum “Science and Society”
Research and Education, St. Petersburg, Russia, June 2008
D. Bimberg
Quantum dot semiconductor optical amplifiers
for wavelength conversion using cross-gain modulation
10th Anniversary Int. Conf. on Transparent Optical Networks
(ICTON 2008), Athens, Greece, June 2008
D. Bimberg
Flying Q-bits and entangled photons for quantum cryptography
Int. Nano-Optoelectronic Workshop (INOW 2008),
Tokyo, Japan, August 2008
D. Bimberg
Controlled variation of excitonic fine structure splitting
in single quantum dots for future single Q-bit and entangled
photon emitters
The 22nd General Conference of the Condensed Matter Division of the
European Physical Society (CMD-22), Rome, Italy, August 2008
D. Bimberg
Low dimensional photonic devices
Asia-Pacific Optical Communications (APOC),
Hangzhou, China, October 2008
D. Bimberg
Semiconductor nanostructures for photonics systems of the future
Rusnanotech: Nanotechnology International Forum,
Moscow, Russia, December 2008
M. Geller
Low Dimensional Semiconductor Devices (LDSD),
San Andres, Columbia, April 2007
M. Geller
Novel nano-flash memories based on quantum dots
15th Int. Winterschool on New Developments in Solid State Physics,
Bad Hofgastein, Austria, February 2008
F. Hopfer
High-speed directly and indirectly modulated VCSELs
20th Int. Conf. on Indium Phosphide and Related Materials
(IPRM 2008), Versailles, France, May 2008
J. Kim
Role of carrier reserviors on the slow phase recovery
of quantum dot semiconductor optical amplifiers
Int. Workshop on Semiconductor Quantum Dot Devices and
Applications, Rennes, France, July 2008
65
M. Laemmlin
High speed optical amplification based on
quantum dots for the 100 G Ethernet
Nonlinear Photonics (NP 2007) OSA-Topical Meeting,
Quebec, Canada, September 2007
N.N. Ledentsov
Novel concepts for ultrahigh-speed quantum-dot
VCSELs and edge-emitters
Photonics West 2007,
N.N. Ledentsov
Submonolayer quantum dots for high speed
surface emitting lasers
14th Semiconducting and Insulating Materials Conference,
Fayetteville, Arkansas, USA, May 2007
N.N. Ledentsov
Quantum dot lasers & new device concepts for
high-brightness applications
Workshop at the World Photonics Congress and Laser 2007 Fair,
Munich, Germany, June 2007
N.N. Ledentsov
Ultrahigh–speed electrooptically–modulated VCSELs:
Modeling and experimental results
Photonics West 2008 (OPTO 2008),
N.N. Ledentsov
Ultrahigh speed surface emitting quantum dot lasers
Int. Semiconductor Laser Conference (ISLC 2008),
Sorrent, Italy, September 2008
C. Meuer
Multi wavelength ultrahigh frequency amplification
by quantum dot semiconductor optical amplifiers
9th Int. Conference on Transparent Optical Networks (ICTON 2007),
Rome, Italy, July 2007
C. Meuer
Nonlinear properties of quantum dot semiconductor optical
amplifiers at 1.3 μm
Frontiers in Optics 2008, Laser Science XXIV,
Rochester, New York, USA, October 2008
U.W. Pohl
InGaAs/GaAs quantum dots for 1.3 µm applications
Long Wavelength Quantum Dots Conference (LWQD 2007) –
Growth and Applications, Rennes, France, July 2007
U.W. Pohl
Quantum dots for single-photon sources
Tyndall Photonics Seminar, University College Cork,
Cork, Ireland, October 2007
66
U.W. Pohl
Epitaxy of self-organized quantum dots
Post Graduate School “Semiconductor-Nanophotonics”,
Berlin, Germany, May 2008
U.W. Pohl
InGaAs quantum dots for electrically driven
single-photon sources
Seminar of the Optoelectronics Research Centre,
Tampere University, Finland, May 2008
S. Rodt
Flying Q-bits from single quantum dots for
future quantum cryptography
8th Int. Conference on Physics of Light-Matter Coupling in
Nanostructures (PLMCN8), Tokyo, Japan, April 2008
A. Schliwa
Inter-sublevel transitions as fingerprints of structural and
chemical properties of InGaAs QDs
Intersublevel studies in self-assembled semiconductor quantum dots
(ISL 2008), Paris, France, April 2008
A. Strittmatter
Quantum dot semiconductor disk lasers
2nd Workshop on Low-Dimensional Structures: Properties and
Applications, Aveiro, Portugal, January - February 2008
M. Winkelnkemper
Strain engineering to control the optical polarization
in nitride quantum dots
Int. Workshop on Nitride Semiconductors (IWN 2008),
Montreux, France, October 2008
67
9.1.5 PhD theses
Geller, Martin
Investigation of Carrier Dynamics in Self-Organized Quantum
Dots for Memory Devices
12.04.2007
Schliwa, Andrei
Electronic Properties of Self-Organized Quantum Dots
25.04.2007
Schulz, Oliver
Einfluss lokaler Materialmodifikationen auf die Eigenschaften
von Halbleiterlasern
05.06.2007
Seguin, Robert
Electronic Fine Structure and Recombination Dynamics in Single
InAs Quantum Dots
28.01.2008
Winkelnkemper,
Momme
Electronic Structure of Nitride-based Quantum Dots
07.11. 2008
9.1.6 Diploma theses
Wündisch, Clemens
Entwicklung eines optischen Samplingsystems
11.01.2007
Germann, Tim
Quantenpunktstrukturen mittels Alternativ Precursor MOCVD
für kohärente Lichtemitter
11.02.2007
Feucker, Max
Zeitaufgelöste Kathodolumineszenz an einzelnen In(Ga)As/GaAs
Quantenpunkten
28.09.2007
Liebich, Sven
Optische Halbleiterverstärker mit Quantenpunkten
26.02.2008
Nowozin, Tobias
Schreib- und Löschzeiten in quantenpunktbasierten
Speicherbausteinen
09.05.2008
Münnix,
Michael Christopher
Quantenpunktbasierte Einzelphotonenquellen
16.06.2008
Siebert, Elisabeth
Anregungsspektroskopie an einzelnen Quantenpunkten
01.07.2008
Stubenrauch, Mirko
Modellierung photonischer Quantenpunktbauelemente
03.07.2008
68
Moser, Philip
Dynamische Eigenschaften von oberflächenemittierenden Lasern
und Modulatoren
17.08.2008
Luckert, Franziska
MOCVD-Wachstum von Sub-Monolagen-Quantenpunkten
26.09.2008
Pohl, Johannes
MOCVD-Wachstum von Quantenpunkt-basierten
Oberflächenemittern
19.12.2008
69
9.1.7 Abstracts of selected papers of department I
1.
Journal of Crystal Growth 298, 567 (2007)
Epitaxy of multimodal InAs/GaAs quantum dot ensembles
K. Pötschke, D. Feise, U.W. Pohl, D. Bimberg
Technische Universität Berlin, Institut für Festkörperphysik,
Sekr. EW 5-2, Hardenbergstr. 36, D-10623 Berlin, Germany
Formation of a multimodal quantum dot (QD) ensemble by strained-layer epitaxy of InAs on
GaAs with a thickness slightly exceeding the critical value for the onset of the 2D–3D
transition is studied. Various growth parameters such as growth rate, growth temperature and
duration of growth interruption after InAs deposition and prior to GaAs cap layer growth were
varied systematically to investigate the effect on the multimodal QD ensemble. Multimodal
features of the QD ensemble are not affected by a change of the InAs growth rate as long as
QD formation starts after deposition. Increase of growth temperature well above 500 °C leads
to a disappearance of multimodal features of the QD ensemble. Tuning of the emission energy
of QD subensembles for fixed QD height is demonstrated by proper adjustment of growth
conditions. Addition of small amounts of antimony supplied during QD growth leads to a
more explicit multimodal structure of the QD ensemble.
6.
Metastable states of surface nanostructure arrays studied
using a Fokker-Planck equation
T.P. Munt1, D.E. Jesson2 V.A. Shchukin3, and D. Bimberg3
1
Department of Physics, School of Engineering and Physical Sciences,
Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
2
School of Physics, Monash University, Victoria 3800, Australia
3
Institut für Festkörperphysik, Technische Universität Berlin, D-10623 Berlin, Germany
We consider the coarsening of surface nanostructures which possess a minimum in formation
energy per atom as a function of island size. The time evolution of the island size distribution
function is evaluated using an approach based on a Fokker-Planck equation. Competition
between chemical potential driven drift and thermal diffusive broadening of the island size
distribution results in narrow Gaussian-like metastable states. The existence of these states,
which allow the possibility of tuning the mean island size through the incorporation of a
deposition flux, depends only upon the presence of a positive gradient in island chemical
potential with respect to island size. Such behavior has important implications for the
fabrication of uniformly sized quantum dot arrays with size selectivity.
70
13.
Journal of Lightwave Technology 26 (9-12), 1540 (2008)
Progress in epitaxial growth and performance
of quantum dot and quantum wire lasers
N.N. Ledentsova, D. Bimbergb, and Z.I. Alferova
a
Abraham Ioffe Physical Technical Institute, Politekhnicheskaya 26,
194021 St. Petersburg, Russia
b
We report on interplay of epitaxial growth phenomena and device performance in quantum
dot (QD) and quantum wire (QWW) lasers based on self-organized nanostructutres. InAs
QDs are the most explored model system for basic understanding of “near-ideal” QD devices.
Vertically-coupled growth of QDs and activated phase separation allow ultimate QD
wavefunction engineering enabling GaAs lasers beyond 1400 nm and polarization-insensitive
optical amplification. A feasibility of QD semiconductor optical amplifiers at terabit
frequencies using InAs QDs is manifested at 1300 and 1500 nm. 1250–1300 nm QD GaAs
edge emitters and VCSELs operate beyond 10 Gb/s with ultimate temperature robustness.
Furthermore, temperature-insensitive operation without current or modulation voltage
adjustment at >20 Gb/s is demonstrated up to ~90 °C. Light-emitting devices based on
InGaN-QDs cover ultraviolet (UV) and visible blue-green spectral ranges. In these
applications, InN-rich nanodomains prevent diffusion of nonequilibrium carries towards
crystal defects and result in advanced degradation robustness of the devices. All the features
characteristic to QDs are unambiguously confirmed for InGaN structures. For the red spectral
range InGaAlP lasers are used. Growth on misoriented surfaces, characteristic to these
devices, leads to nano-periodically-step-bunched epitaxial surfaces resulting in two principal
effects: 1) step-bunch-assisted alloy phase separation, leading to a spontaneous formation of
ordered natural superlattices; 2) formation of quantum wire-like structures in the active region
of the device. A high degree of polarization is revealed in the luminescence recorded from the
top surface of the structures, in agreement with the QWW nature of the gain medium. QD and
QWW lasers are remaining at the frontier of the modern optoelectronics penetrating into the
mainstream applications in key industries.
71
14.
Journal of Crystal Growth 310, 5182 (2008)
Quantum-dot semiconductor disk lasers
T.D. Germanna, A. Strittmattera, U.W. Pohla, D. Bimberga,
J. Rautiainenb, M. Guinab, O.G. Okhotnikovb
a
Institut für Festkörperphysik, Technische Universität Berlin, Germany
b
Optoelectronics Research Centre, Tampere University of Technology, Finland
We demonstrate quantum-dot (QD)-based, optically pumped semiconductor disk lasers
(SDLs) for wavelengths ranging from 950 to 1210 nm. QDs grown either in the submonolayer
(SML) or in the Stranski–Krastanow (SK) regime are employed as active layers of the SDLs
which are based on two different design concepts. Output power of up to 1.4W continuous
wave (CW) is achieved with an InAs/ GaAs-SML SDL at 1040 nm. Up to 21 InGaAs SK-QD
layers within a single SDL gain structure are used to realize the ground-state CW lasing with
0.3W at 1210 nm. The SK-QD-based SDL shows temperature and pump-power stable
emission. Threshold and differential efficiency do not depend on heat-sink temperature.
18.
Appl. Phys. Lett. 91, 242109 (2007)
106 years extrapolated hole storage time in GaSb/AlAs quantum dots
A. Marent, M. Geller, A. Schliwa, D. Feise, K. Pötschke, and D. Bimberg
Institut für Festkörperphysik, Technische Universität Berlin,
Hardenbergstrasse 36, 10623 Berlin, Germany
N. Akçay and N. Öncan
Department of Physics, Faculty of Science, Istanbul University,
Vezneciler, 34134 Istanbul, Turkey
A thermal activation energy of 710 meV for hole emission from InAs/GaAs quantum dots
(QDs) across an Al0.9Ga0.1As barrier is determined by using time-resolved capacitance
spectroscopy. A hole storage time of 1.6 s at room temperature is directly measured, being
three orders of magnitude longer than a typical dynamic random access memory (DRAM)
refresh time. The dependence of the hole storage time in different III–V QDs on their
localization energy is determined and the localization energies in GaSb-based QDs are
calculated using eight-band k·p theory. A storage time of about 106 years in GaSb/AlAs QDs
is extrapolated, sufficient for a QD-based nonvolatile (flash) memory.
72
23.
Impact of size, shape, and composition on piezoelectric effects and
electronic properties of In(Ga)As/GaAs quantum dots
A. Schliwa, M. Winkelnkemper, and D. Bimberg
The strain fields in and around self-organized In(Ga)As/GaAs quantum dots (QDs) sensitively
depend on QD geometry, average InGaAs composition, and the In/Ga distribution profile.
Piezoelectric fields of varying sizes are one result of these strain fields. We study
systematically a large variety of realistic QD geometries andcomposition profiles, and
calculate the linear and quadratic parts of the piezoelectric field. The balance of the two
orders depends strongly on the QD shape and composition. For pyramidal InAs QDs with
sharp interfaces, a strong dominance of the second-order fields is found. Upon annealing, the
first-order terms become dominant, resulting in a reordering of the electron p and d states and
a reorientation of the hole wave functions.
26.
Journal of Applied Physics 101, 113708 (2007)
Polarized emission lines from A- and B-type excitonic complexes
in single InGaN/GaN quantum dots
M. Winkelnkemper
and Fritz-Haber-Institut der Max-Planck-Gesellschaft, D-14195 Berlin, Germany
R. Seguin, S. Rodt, A. Schliwa, L. Reißmann, A. Strittmatter, A. Hoffmann, and D. Bimberg
Cathodoluminescence measurements on single InGaN/GaN quantum dots (QDs) are reported.
Complex spectra with up to five emission lines per QD are observed. The lines are polarized
along the orthogonal crystal directions [11-20] and [-1100]. Realistic eight-band
k•p electronic structure calculations show that the polarization of the lines can be explained
by excitonic recombinations involving hole states which are formed either by the A or the B
valence band.
73
32.
Appl. Phys. Lett. 92, 092108 (2008)
A write time of 6 ns for quantum dot–based memory structures
M. Gellera, A. Marenta, T. Nowozina, D. Bimberga , N. Akçayb, and N. Öncanb
a
b
Department of Physics, Faculty of Science, Istanbul University,
34134 Vezneciler, Istanbul, Turkey
The concept of a memory device based on self-organized quantum dots (QDs) is presented,
enabling extremely fast write times, limited only by the charge carrier relaxation time being in
the picosecond range. For a first device structure with embedded InAs/GaAs QDs, a write
time of 6 ns is demonstrated. A similar structure containing GaSb/GaAs QDs shows a write
time of 14 ns. These write times are independent of the localization energy (e.g., storage time)
of the charge carriers and at the moment are limited only by the experimental setup and the
parasitic cutoff frequency of the RC low pass of the device.
33.
Consistent set of band parameters
for the group-III nitrides AlN, GaN, and InN
P. Rinke1, M. Winkelnkemper1, 2, A. Qteish3, D. Bimberg2, J. Neugebauer4,
and M. Scheffler1
1
Fritz-Haber-Institut der Max-Planck-Gesellschaft,
Faradayweg 4-6, D-14195 Berlin, Germany
2
Hardenbergstraße 36, D-10623 Berlin, Germany
3
Department of Physics, Yarmouk University, 21163-Irbid, Jordan
4
Department of Computational Materials Design, Max-Planck-Institut fur Eisenforschung,
D-40237 Düsseldorf, Germany
We have derived consistent sets of band parameters (band gaps, crystal field splittings, bandgap deformation potentials, effective masses, and Luttinger and EP parameters) for AlN, GaN,
and InN in the zinc-blende and wurtzite phases employing many-body perturbation theory in
the G0W0 approximation. The G0W0 method has been combined with density-functional theory
(DFT) calculations in the exact-exchange optimized effective potential approach to overcome
the limitations of local-density or gradient-corrected DFT functionals. The band structures in
the vicinity of the Г point have been used to directly parametrize a 4 X 4 k•p Hamiltonian to
capture nonparabolicities in the conduction bands and the more complex valence-band
structure of the wurtzite phases. We demonstrate that the band parameters derived in this
fashion are in very good agreement with the available experimental data and provide reliable
predictions for all parameters, which have not been determined experimentally so far.
74
34.
Appl. Phys. Lett. 92, 063116 (2008)
Decay dynamics of neutral and charged excitonic complexes
M. Feucker, R. Seguin, S. Rodt, A. Hoffmann, and D. Bimberg
Systematic time-resolved measurements on neutral and charged excitonic complexes (X, XX,
X+, and XX+) of 26 different single InAs/GaAs quantum dots are reported. The ratios of the
decay times are discussed in terms of the number of transition channels determined by the
excitonic fine structure and a specific transition time for each channel. The measured ratio for
the neutral complexes is 1.7 deviating from the theoretically predicted value of 2. A ratio of
1.5 for the positively charged exciton and biexciton decay time is predicted and exactly
matched by the measured ratio indicating identical specific transition times for the transition
channels involved.
37.
J. Phys.: Condens. Matter 20, 454211 (2008)
GaN/AlN quantum dots for single qubit emitters
M. Winkelnkemper, R. Seguin, S. Rodt, A. Hoffmann, and D. Bimberg
Hardenbergstraße 36, D-10623 Berlin, Germany
We study theoretically the electronic properties of c-plane GaN/AlN quantum dots (QDs)
with the focus on their potential as sources of single polarized photons for future quantum
communication systems. Within the framework of eight-band k•p theory we calculate the
optical interband transitions of the QDs and their polarization properties. We show that an
anisotropy of the QD confinement potential in the basal plane (e.g. QD elongation or strain
anisotropy) leads to a pronounced linear polarization of the ground-state and excited-state
transitions. An externally applied uniaxial stress can be used to either induce a linear
polarization of the ground-state transition for emission of single polarized photons or even to
compensate the polarization induced by the structural elongation.
75
38.
Impact of Coulomb scattering on the ultrafast gain recovery
in InGaAs quantum dots
J. Gomis-Bresco, S. Dommers, V.V. Temnov, and U. Woggon
Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623 Berlin, Germany
M. Laemmlin and D. Bimberg
Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin, Germany
E. Malić, M. Richter, E. Schöll, and A. Knorr
Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
The application of quantum dot (QD) semiconductor optical amplifiers (SOAs) in above 100Gbit Ethernet networks demands an ultrafast gain recovery on time scales similar to that of
the input pulse ~100 GHz repetition frequency. Microscopic scattering processes have to act
at shortest possible time scales and mechanisms speeding up the Coulomb scattering have to
be explored, controlled, and exploited. We present a microscopic description of the gain
recovery by coupled polarization- and population dynamics in a thermal nonequilibrium
situation going beyond rate-equation models and discuss the limitations of Coulomb
scattering between 0D and 2D-confined quantum states. An experiment is designed which
demonstrates the control of gain recovery for THz pulse trains in InGaAs QD-based SOAs
under powerful electrical injection.
41.
Applied Surface Science 225, 799 (2008)
Onion-like growth and inverted many-particle energies in quantum dots
D. Bimberg
Use of surfactants like antimony in MOCVD growth enables novel growth regimes for
quantum dots (QDs). The quantum dot ensemble luminescence no longer appears as a single
inhomogeneously broadened peak but shows a multimodal structure. Quantum dot
subensembles are forming which differ in height by exactly one monolayer. For the first time
the systematic dependence of excitonic properties on quantum dot size and shape can be
investigated in detail. Both biexcitonic binding energy and excitonic fine-structure splitting
vary from large positive through zero to negative values. Correlation and piezoelectric effects
explain the observations.
76
Adances in Solid State Physics 46, 45 (2008)
45.
Size-tunable exchange interaction in InAs/GaAs quantum dots
U.W. Pohl, A. Schliwa, R. Seguin, S. Rodt, K. Pötschke, and D. Bimberg
Hardenbergstr. 36, 10623 Berlin, Germany
Single epitaxial quantum dots are promising candidates for the realization of quantum
information schemes due to their atom-like electronic properties and the ease of integration
into optoelectronic devices. Prerequisite for realistic applications is the ability to control the
excitonic energies of the dot. A major step in this direction was recently reached by advanced
self-organized quantum-dot growth, yielding ensembles of equally shaped InAs/GaAs dots
with a multimodal size distribution. The well-defined sizes of spectrally well separated
subensembles enable a direct correlation of structural and excitonic properties, representing
an ideal model system to unravel the complex interplay of Coulomb interaction and the
quantum dot’s confining potential that depends on size, shape, and composition. In this paper
we focus on the exciton-biexciton system with emphasis on the excitonic fine-structure
splitting. Across the whole range of size variations within our multimodal quantum dot
distribution a systematic trend from +520 μeV to −80 μeV is found for decreasing dot size.
To identify the underlying effects calculations of the fine-structure splitting are performed. A
systematic variation of the structural and piezoelectric properties of the modeled quantum
dots excludes shape anisotropy and tags piezoelectricity as a key parameter controlling the
fine-structure splitting in our quantum dots.
Phys. Stat. Sol. (c) 4 (2), 547 (2007)
48.
Electrically driven quantum dot single photon source
A. Lochmann1, E. Stock1, O. Schulz1, F. Hopfer1, D. Bimberg1, V.A. Haisler1, 2,
A.I. Toropov2, A.K. Bakarov2, M. Scholz3, S. Büttner3, and O. Benson3
1
Technische Universität Berlin, Institut für Festkörperphysik and Center for NanoPhotonics,
Sekr. EW 5-2, Hardenbergstr. 36, 10623 Berlin, Germany
2
Institute of Semiconductor Physics, Lavrenteva avenue 13, 630090 Novosibirsk, Russia
3
Institut für Physik, Humboldt Universität zu Berlin,
Hausvogteiplatz 5-7, 10117 Berlin, Germany
We report on a miniature solid state emitter structure, which allows electrical pumping of
only one single InAs quantum dot (QD) grown in the Stranski-Krastanow mode. The emitter
demonstrates a strongly monochromatic polarized emission of a single QD exciton.
Correlation measurements of the emitted photons show a clear antibunching behavior. The
structure is thus attractive for practical implementation as effective single photon source for
quantum cryptography.
77
49.
Appl. Phys. Lett. 91, 241112 (2007)
High-power wavelength stabilized 970 nm tilted cavity laser
with a 41.3 dB side mode suppression ratio
L.Ya. Karachinsky, M. Kuntz, G. Fiol, V.A. Shchukin, N.N. Ledentsov, and D. Bimberg
EW 5-2, Hardenbergstr. 36, D-10623 Berlin, Germany
A.R. Kovsh and S.S. Mikhrin
Innolume GmbH, Konrad-Adenauer-Allee 11, 44263 Dortmund, Germany
I.I. Novikov, Yu.M. Shernyakov, and M.V. Maximov
A.F.Ioffe Physico-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg, Russia
We studied wavelength stabilized all-epitaxial 970 nm spectral range GaAs/GaAlAs tilted
cavity lasers (TCLs). Single transverse mode edge-emitting 4-µm-wide ridge lasers
demonstrated spatial and spectral single mode continuous wave operation with a longitudinal
side mode suppression ratio up to 41.3 dB. Small signal modulation bandwidth of 3 GHz with
a resonance peak of 6 dB at the relaxation oscillation frequency was measured for a 870 µm
long device. TCL modulation efficiency is 0.36 GHz/ (mA)1/2. S-parameter measurements
indicate that much higher frequencies may be expected in case of more advanced processing
and/or shorter cavity lengths.
51.
Semicond. Sci. Technol. 22, 380 (2007)
Resonance wavelength in planar multilayer waveguides:
Control and complete suppression of temperature sensitivity
M.B. Lifshits1,2, V.A. Shchukin1,3, N.N. Ledentsov1,3, and D. Bimberg1
1
2
Abraham Ioffe Physical Technical Institute, 194021 St. Petersburg, Russia
3
on leave from Abraham Ioffe Physical Technical Institute
We report the possibility of realizing complete thermal stabilization of the resonance
transparency wavelength λchar in a planar multilayer tilted cavity waveguide. When the
positive temperature coefficient of the refractive index dn/dT is a nonlinear function of the
alloy composition, which is the case in most semiconductor alloys, there exists the possibility
of achieving complete control of the resonance transparency wavelength. The thermal shift
dλchar/dT can be positive, zero or negative. Our result applies quite generally to optical
waveguides, etalons, filters, semiconductor lasers and optical amplifiers, potentially extending
the performance of the devices and their application range.
78
56.
High-power low-beam divergence edge-emitting semiconductor lasers with
1- and 2-D photonic bandgap crystal waveguide
M.V. Maximov1, 2, Y.M. Shernyakov1, 2, I.I. Novikov2, N.Yu. Gordeev2, L.Ya. Karachinsky2,
3
, U. Ben-Ami4, D. Bortman-Arbiv4, A. Sharon4, V.A. Shchukin3, 5, N.N. Ledentsov3, 5,
T. Kettler3, K. Posilovic3, and D. Bimberg3
1
St. Petersburg Physics and Technology Center for Research and Education, Russian
Academy of Sciences, St. Petersburg 195220, Russia
2
A. F. Ioffe Physico-Technical Institute, Russian Academy of Sciences,
St. Petersburg, 194021, Russia
3
Institute for Solid State Physics, Technical University of Berlin, D-10623 Berlin, Germany
4
Photonic Bandgap Crystal (PBC) Lasers, Ltd., P.O. Box 186, Kibbutz Einat 49910, Israel
5
VI Systems GmbH, Hardenbergstr. 7, D-10623 Berlin
We report on edge-emitting lasers based on the 1- and 2-D longitudinal photonic bandgap
crystal concept. The longitudinal photonic bandgap crystal (PBC) design allows a robust and
controllable extension of the fundamental mode over a thick multilayer waveguide to obtain a
very large vertical mode spot size and a narrow vertical beam divergence. We focus on highperformance PBC lasers in different material systems. Ridge 658 nm GaInP–AlGaInP singlemode PBC lasers demonstrate vertical beam divergence of 8° and continuous-wave (CW)
output power above 115 mW. Multimode CW power of 500 mW is achieved at 635 nm in
50-μm-wide lasers. GaAs/AlGaAs PBC lasers emitting at 850 nm show a vertical far-field
divergence of 9°, differential quantum efficiency of 95%, and maximum CW single mode
power of 270 mW. InGaAs/AlGaAs PBC lasers emitting at 980 nm show a vertical far-field
of 4° and single-mode output power of 1.2 W. Two-dimensional PBClasers based on fieldcoupled multiridge arrays show stable single lateral mode operation with narrow lateral farfield of 0.6 and output power in pulsed mode of 20 W. Maximal CW output power in single
lateral mode operation is 2.7 W.
60.
Electr. Lett. 44 (3), 168 (2008)
Quantum dot based nanophotonics and nanoelectronics
D. Bimberg
Institute of Solid State Physics and Center of NanoPhotonics, Technische Universität Berlin,
Hardenbergstr. 36, 10623 Berlin, Germany
Invention of non-disruptive fabrication technologies for semiconductor quantum dots
presented a dream for generations of semiconductor device engineers. Today such
technologies exist. A wealth of completely novel devices and such with dramatically
improved properties based either on a single/few or a large density of quantum dots appears.
Among them are single q-bit emitters, nano-flash memories, ultrafast lasers and amplifiers
enabling a wealth of advanced systems.
79
63.
Appl. Phys. Lett. 93, 221102 (2008)
Ultrahigh-brightness 850 nm GaAs/AlGaAs photonic crystal laser diodes
K. Posilovic1, T. Kettler1, V.A. Shchukin1, N.N. Ledentsov1, U.W. Pohl1, D. Bimberg1,
J. Fricke2, A. Ginolas2, G. Erbert2, G. Tränkle2, J. Jönsson3, and M. Weyers3
1
EW5-2, Hardenbergstr. 36, 10623 Berlin, Germany
2
Ferdinand-Braun-Institut für Höchstfrequenztechnik,
Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
3
TESAG, Three-Five Epitaxial Services AG, Kekulé-Str. 2-4, 12489 Berlin, Germany
One-dimensional photonic crystal lasers emitting in the 850 nm range show high internal
quantum efficiencies of 93% and very narrow vertical beam divergence of 7.1° (full width at
half maximum) 50 µm broad area lasers with unpassivated facets exhibit a high total output
power of nearly 20 W in pulsed mode with a divergence of 9.5 x 11.3° leading to a record
brightness of 3 x 108 W cm-2 sr-1, being presently the best value ever reported for a single
broad area laser diode. 100 µm broad devices with unpassivated facets show continuous wave
operation with an output power of 1.9 W.
65.
Coulomb damped relaxation oscillations in
semiconductor quantum dot lasers
E. Malić1, M.J.P. Bormann1, P. Hövel1, M. Kuntz2 D. Bimberg2,
A. Knorr1, and E. Schöll1
1
Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
2
Institut für Festkörperphysik and Center of Nanophotonics,
Technische Universität Berlin, 10623 Berlin, Germany
We present a theoretical simulation of the turn-on dynamics of InAs/GaAs quantum dot
semiconductor lasers driven by electrical current pulses. Our approach goes beyond standard
phenomenological rate equations. It contains microscopically calculated Coulomb scattering
rates, which describe Auger transitions between quantum dots and the wetting layer. In
agreement with the experimental results, we predict a strong damping of relaxation
oscillations on a nanosecond time scale. We find a complex dependence of the Coulomb
scattering rates on the wetting layer electron and hole densities, and we show their crucial
importance for the understanding of the turn-on dynamics of quantum dot lasers.
80
66.
Optics Express 15 (9), 5388 (2007)
Direct correlation between a highly damped modulation response
and ultra low relative intensity noise in an InAs/GaAs quantum dot laser
A. Capua1, L. Rozenfeld1, V. Mikhelashvili1, and G. Eisenstein1, M. Kuntz2,
M. Laemmlin2, and D. Bimberg2
1
Electrical Engineering Department, Technion, Haifa 32000, Israel
2
We describe modulation responses and relative intensity noise (RIN) spectra of an InAs/GaAs
quantum dot laser operating near 1300 nm. A very large nonlinear gain compression
coefficient yields a highly damped modulation response with a maximum 3 dB bandwidth of
~6.5 GHz and flat RIN spectra which reach as low a level as –158÷–160 dB/Hz at frequencies
up to 10 GHz.
68.
Proc. of the IEEE, Optoelectronic Devices based on Quantum Dots 95 (9), 1741 (2007)
High-speed quantum-dot vertical-cavity surface-emitting lasers
N.N. Ledentsov1, 2, F. Hopfer1, and D. Bimberg1
1
2
on leave from Abraham Ioffe Physical Technical Institute
We report on recent progress in high-speed quantum-dot (QD) vertical-cavity surfaceemitting lasers (VCSELs). Advanced types of QD media allow an ultrahigh modal gain, avoid
temperature depletion, and gain saturation effects. Temperature robustness up to 100 °C for
0.96 – 1.25 µm range devices is realized in the continuous wave (cw) regime. An open eye
20 Gb/s operation with bit error rates better than 10-12 has been achieved in a temperature
range 25 °C – 85 °C without current adjustment. A different approach for ultrahigh-speed
operation is based on a combination of the VCSEL section, operating in the CW mode with
an additional section of the device, which is electrooptically modulated under a reverse bias.
The tuning of a resonance wavelength of the second section, caused by the electrooptic effect,
affects the transmission of the system. The approach enables ultrahighspeed signal
modulation. 60 GHz electrical and ~35 GHz optical (limited by the photodetector response)
bandwidths are realized.
81
69.
Proc. of the IEEE, Optoelectronic Devices based on Quantum Dots 95 (9), 1767 (2007)
High-speed mode-locked quantum-dot lasers and optical mplifiers
M. Kuntz, G. Fiol, M. Laemmlin, C. Meuer, and D. Bimberg
Recent results on GaAs-based high-speed mode-locked quantum-dot (QD) lasers and optical
amplifiers with an operation wavelength centered at 1290 nm are reviewed and their complex
dependence on device and operating parameters is discussed on the basis of experimental data
obtained with integrated fiber-based QD device modules. Hybrid and passive mode locking of
QD lasers with repetition frequencies between 5 and 80 GHz, sub-ps pulse widths, ultralow
timing jitter down to 190 fs, high output peak power beyond 1 W, and suppression of
Q-switching are reported, showing the large potential of this class of devices for O-band
optical fiber applications. Results on cw and dynamical characterization of QD semiconductor
optical amplifiers (SOAs) are presented. QD amplifiers exhibit a close-to-ideal noise figure of
4 dB and demonstrate multiwavelength amplification of three coarse wavelength division
multiplexing (CWDM) wavelengths simultaneously. Modelling of QD polarization
dependence shows that it should be possible to achieve polarization insensitive SOAs using
vertically coupled QD stacks. Amplification of ultrafast 80 GHz optical combs and bit-errorfree data signal amplification at 40 Gb/s with QD SOAs show the potential for their
application in future 100 Gb Ethernet networks.
73.
Electr. Lett. 44 (22),1305 (2008)
120 °C 20 Gbit/s operation of 980 nm VCSEL
A. Mutig1, G. Fiol1, P. Moser1, D. Arsenijevic1, V.A. Shchukin1, 3, N.N. Ledentsov1, 3,
S.S. Mikhrin2, I.L. Krestnikov2, D.A. Livshits2, A.R. Kovsh2, F. Hopfer1 , and D. Bimberg1
1
Institute of Solid State Physics and Center for NanoPhotonics,
Technische Universität Berlin, Hardenbergstr. 36, Berlin 10623, Germany
2
Innolume GmbH, Konrad-Adenauer-Allee 11, Dortmund 44263, Germany
3
VI Systems GmbH, Hardenbergstr. 7, Berlin, D-10623, Germany
980 nm VCSELs show under 20 Gbit/s large signal modulation clearly open eyes without
adjustment of the driving conditions between 0 and 120°C.
82
74.
Appl. Phys. Lett. 93, 051110 (2008)
40 GHz small-signal cross-gain modulation
in 1.3 µm quantum dot semiconductor optical amplifiers
C. Meuer1, J. Kim1, M. Laemmlin1, S. Liebich1, D. Bimberg1, A. Capua2, G. Eisenstein2,
R. Bonk3, T. Vallaitis3, J. Leuthold3, A.R. Kovsh4, and I.L. Krestnikov4
1
EW 5-2, Hardenbergstr. 36, 10623 Berlin, Germany
2
Electrical Engineering Department, Technion, Haifa 32000, Israel
3
Institut für Hochfrequenztechnik und Quantenelektronik, Universität Karlsruhe,
Engesserstr. 5, 76131 Karlsruhe, Germany
4
Innolume GmbH, Konrad-Adenauer-Allee 11, 44263 Dortmund, Germany
Small-signal cross-gain modulation of quantum dot based semiconductor optical amplifiers
(QD SOAs), having a dot-in-a-well structure, is presented, demonstrating superiority for
ultrahigh bit rate wavelength conversion. Optimization of the QD SOA high speed
characteristics via bias current and optical pump power is presented and a small-signal 3 dB
bandwidth exceeding 40 GHz is demonstrated. The p-doped samples investigated here enable
small-signal wavelength conversion within a range of 30 nm, limited mainly by the gain
bandwidth.
88.
Optics Express 16 (11), 8269 (2008)
Static gain saturation in quantum dot semiconductor optical amplifiers
C. Meuer1, J. Kim1, M. Laemmlin1, S. Liebich1, A. Capua2,
G. Eisenstein1,2, A.R. Kovsh3, S.S. Mikhrin3, I.L. Krestnikov3,
and D. Bimberg1
1
EW 5-2, Hardenbergstr. 36, 10623 Berlin, Germany
2
Electrical Engineering Department, Technion, Haifa 32000 Israel
3
Innolume GmbH, Konrad-Adenauer-Allee 11, 44263 Dortmund
Measurements of saturated amplified spontaneous emissionspectra of quantum dot
semiconductor optical amplifiers demonstrate efficient replenishment of the quantum-dot
ground state population from excited states. This saturation behavior is perfectly modeled by
a rate equation model. We examined experimentally the dependence of saturation on the drive
current and the saturating optical pump power as well as on the pump wavelength. A coherent
noise spectral hole is observed with which we assess dynamical properties and propose
optimization of the SOA operating parameters for high speed applications.
83
91.
Proc. of SPIE: Physics and Simulation of Optoelectronic Devices 6889, OH-1 (2008)
Ultrahigh–speed electrooptically–modulated VCSELs:
Modeling and experimental results
V.A. Shchukin1, 2, 3, N.N. Ledentsov1, 2, 3, J.A. Lott1, H. Quast1, F. Hopfer2,
L.Ya. Karachinsky 2, 3, M. Kuntz2 , P. Moser2, A. Mutig2, A. Strittmatter2,
V.P. Kalosha4, and D. Bimberg2
1
VI Systems GmbH, Hardenbergstr. 7, D–10623 Berlin, Germany
2
Institut für Festkörperphysik and Center of NanoPhotonics, Technische Universität Berlin,
EW 5–2, Hardenbergstr. 36, D–10623 Berlin, Germany
3
Abraham Ioffe Physical Technical Institute,
Politekhnicheskaya 26, 194021 St. Petersburg, Russia
4
Department of Physics, University of Ottawa, 150 Louis Pasteur,
Ottawa ON K1N6N5, Canada
We have studied the modulation properties of a vertical cavity surface–emitting laser
(VCSEL) coupled to an electrooptical modulator. It is shown that, if the modulator is placed
in a resonant cavity, the modulation of the light output power is governed predominantly by
electrooptic, or electrorefraction effect rather than by electroabsorption. A novel concept of
electrooptically modulated (EOM) VCSEL based on the stopband edge–tunable distributed
Bragg reflector (DBR) is proposed which allows overcoming the limitations of the first–
generation EOM VCSEL based on resonantly coupled cavities. A new class of electrooptic
(EO) media is proposed based on type–II heterostructures, in which the exciton oscillator
strength increases from a zero or a small value at zero bias to a large value at an applied bias.
A EOM VCSEL based on a stopband–edge tunable DBR including a type–II EO medium is to
show the most temperature–robust operation. Modeling of a high–frequency response of a
VCSEL light output against large signal modulation of the mirror transmittance has
demonstrated the feasibility to reach 40 Gb/s operation at low bit error rate. EOM VCSEL
showing 60 GHz electrical and ~35 GHz optical (limited by the photodetector response)
bandwidths is realized.
84
97.
J. of Phys.: Condens. Matter 20, 164202 (2008)
Phase and amplitude response of the ‘0.7 feature’ caused by holes
in silicon one-dimensional wires and rings
N.T. Bagraev1, N.G. Galkin1,W. Gehlhoff2, L.E. Klyachkin1, and A.M. Malyarenko1
1
Ioffe Physico-Technical Institute, RAS, 194021 St Petersburg, Russia
2
Institut für Festkörperphysik, TU Berlin, D-10623 Berlin, Germany
We present findings for the 0.7(2e2/h) feature in the hole quantum conductance staircase that
is caused by silicon one-dimensional channels prepared by the split-gate method inside the ptype silicon quantum well (SQW) on the n-type Si(100) surface. Firstly, the interplay of the
spin depolarization with the evolution of the 0.7(2e2/h) feature from the e2/h to 3/2 e2/h values
as a function of the sheet density of holes is revealed by the quantum point contact connecting
two 2D reservoirs in the p-type SQW. The 1D holes are demonstrated to be spin polarized at
low sheet density, because the 0.7(2e2/h) feature is close to the value of 0.5(2e2/h) that
indicates the spin degeneracy lifting for the first step of the quantum conductance staircase.
The 0.7(2e2/h) feature is found to take, however, the value of 0.75(2e2/h) when the sheet
density increases, thereby giving rise to the spin depolarization of the 1D holes. Secondly, the
amplitude and phase sensitivity of the 0.7(2e2/h) feature are studied by varying the value of
the external magnetic field and the top-gate voltage that are applied perpendicularly to the
plane of the double-slit ring embedded in the p-type SQW, with the extra quantum point
contact inserted in the one of its arms. The Aharonov–Bohm and the Aharonov–Casher
conductance oscillations obtained are evidence of the interplay of the spontaneous spin
polarization and the Rashba spin–orbit interaction (SOI) in the formation of the 0.7(2e2/h)
feature. Finally, the variations of the 0.7(2e2/h) feature caused by the Rashba SOI are found to
take in the fractional form with both the plateaus and steps as a function of the top-gate
voltage.
85
100.
Journal of Applied Physics 103, 07D140 (2008)
Surface modification of Co-doped ZnO nanocrystals
and its effects on the magnetic properties
A.S. Pereira
Departamento de Química and CICECO, Universidade de Aveiro,
P-3810-193 Aveiro, Portugal
A.O. Ankiewicz
I3 N-Institute for Nanostructures, Nanomodelling and Nanomanufacturing and Departamento
de Física, Universidade de Aveiro, P-3810-193 Aveiro, Portugal
and Institut für Experimentelle Physik II, Universität Leipzig, D-04103 Leipzig, Germany
W. Gehlhoff and A. Hoffmann
S. Pereira and T. Trindade
CICECO, Universidade de Aveiro, P-3810-193 Aveiro, Portugal
M. Grundmann
Institut für Experimentelle Physik II, Universität Leipzig, D-04103 Leipzig, Germany
M.C. Carmo and N.A. Sobolev
de Física, Universidade de Aveiro, P-3810-193 Aveiro, Portugal
A series of chemically prepared Co2+-doped ZnO colloids has been surface modified either by
growing shells of ZnSe or by the in situ encapsulation in poly(styrene). The surface
modification effects using these two distinct chemical strategies on the magnetic properties of
the nanocrystals were probed by electron paramagnetic resonance (EPR). Structural
characterization by means of x-ray diffraction and transmission electron microscopy gave no
evidence of second phase formation within the detection limits of the used equipment. The
EPR analysis was carried out by simulations of the powderlike EPR spectra. The results
confirm that in the core of these nanocrystals Co was incorporated as Co2+, occupying the
Zn2+ sites in the wurtzite structure of ZnO. Additionally we identify two Co signals stemming
from the nanocrystals’ shell. The performed surface modifications clearly change the relative
intensity of the EPR spectrum components, revealing the core and shell signals.
86
87
9.2. Department II
Prof. Dr. rer. nat. Christian Thomsen (Dept. IIa)
Prof. Dr. rer. nat. Janina Maultzsch (Dept. IIa)
Prof. em. Dr.-Ing. Dr. h.c. mult. Immanuel Broser (Dept. IIb)
Priv.-Doz. Dr. Axel Hoffmann (Dept. IIb)
9.2.a Department IIa
Prof. Dr. rer. nat. Janina Maultzsch
9.2a.0 Staff
Secretary
Marianne Heinold (until 08.12.2008)
Mandy Neumann (from 08.12.2008)
Technical staff
Sabine Morgner
Ing.grad. Heiner Perls
Michael Mayer
Senior scientists
Dr. Paula Giudici
Dr. Niculina Peica
Dr. Peter Rafailov
Dr. Harald Scheel
PhD candidates
Dipl.-Phys. Katharina Brose
Dipl.-Phys. Dirk Heinrich
Dipl.-Phys. Sevak Khachadorian
Dipl.-Phys. Holger Lange
Dipl.-Phys. Jan Laudenbach
Dipl.-Phys. Patrick May
Dipl.-Phys. Marcel Mohr
Dipl.-Phys. Matthias Müller
Dipl.-Phys. Grit Petschick
Dipl.-Phys. Nils Rosenkranz
Dipl.-Phys. Hagen Telg
Dipl.-Phys. Norman Tschirner
88
Diploma students (status of 31.12.2008 - thesis completed = c)
Katharina Brose (c)
Max Bügler (c)
David Eckhardt (c)
Martin Fouquet (c)
Roland Gillen
Lars Houpt (c)
Martin Kaiser
Sevak Khachadorian (c)
Ronny Kirste (c)
Martin Kreutzer (c)
Reinhard Meinke
Carola Nisse (c)
Jörg Polte (c)
Nils Rosenkranz (c)
Martin Weiß
Stefan Werner (c)
89
9.2a.1 Summary of activities
The activity of this group is centered around optical spectroscopy of carbon nanotubes, wide
and narrow-gap semiconductors nanostructures, 2D electron gases, quantum and related
systems dots, superconductor-semiconductor-hybrid structures, ferrofluids, and high-Tc
superconductors.
Emphasis in the work on carbon nanotubes and related system was to extend on expertise in
understanding fundamental properties of functionalized carbon nanotube systems and of
graphenes. The full phonon dispersion relations were determined for graphite at the ESRF, a
result that became of vital importance for the renewed interest in single-layer graphite:
graphene.
In the semiconductor nanosystems we focused on theoretical and experimental properties of
CdSe nanorods and Si nanowires. In the Centre of Excellence we worked on carotene and the
photosystems II which contains carotene. Strength of our group continues to be the close
work on theory and experiment.
In 2008 Prof. Dr. Janina Maultzsch joined in Berlin after a prolonged stay at Columbia
University. She now leads a group of several scientists with a research focus on tip- enhanced
Raman spectroscopy. There are close collaborations on several topics between our groups.
90
91
9.2a.2 Publications
The abstracts of papers marked by * are reprinted in section 9.2a.6.
1.
XRD and Raman spectroscopic study of Ru and Os doped Bi12 SiO20 crystals
P.M. Rafailov, A.V. Egorysheva, V.M. Skorikov, R. Petrova, M.N. Veleva, T.D.
Dudkina, C. Thomsen, A.Ya.Vasilev, and M.M. Gospodinov
Journal of Optoelectronics and Advanced Materials 9, 293-295 (2007).
2.*
Evidence of breakdown of the spin symmetry in diluted 2D electron gases
P. Giudici, A.R. Goni, P.G. Bolcatto, C.R. Proetto, C. Thomsen, K. Eberl, and
M. Hauser
Europhysics Letters 77, 37003 (2007)
3.*
Dynamics of magnetic-field-induced clustering in ionic ferrofluides from Raman
scattering
D. Heinrich, A.R. Goni, and C. Thomsen
J. Chem. Phys. 126, 124701 (2007)
4.*
Characterization of Carbon Nanotubes by Optical Spectroscopy
J. Maultzsch and C. Thomsen
Advanced Micro and Nanosystems, Vol. 8: CNT-based Nanosystems; eds. Baltes,
Hierold, (WILEY-VCH, Weinheim, 2008), ISBN: 978-3-527-31720-2
5.
On remote and virtual experiments in eLearning
S. Jeschke, H. Scheel, T. Richter, and C. Thomsen
Journal of Software (JSW) 2, 76-85 (2007)
6.
Dependence of the band-gap pressure coefficients of self-assembled InAs/GaAs
quantum dots on the quantum dot size
C. Kristukat, A.R. Goni, K. Potschke, D. Bimberg, and C. Thomsen
phys. stat. sol. (b) 244, 53-58 (2007)
7.*
Elasticity of single-crystalline graphite: Inelastic x-ray scattering study
A.Bosak, M. Krisch, M. Mohr, J. Maultzsch, and C. Thomsen
Phys. Rev. B 75, 153408 (2007)
8.* Mixing of the fully symmetric vibrational modes in carbon nanotubes
M. Mohr, M. Machón, C. Thomsen, I. Milovsevic, and M. Damnjanovic
Phys. Rev. B 75, 195401 (2007)
9.* The phonon dispersion of graphite by inelastic X-ray scattering
M. Mohr, J. Maultzsch, E. Dobardvzic, S. Reich, I. Milovsevic, M. Damnjanovic, A.
Bosak, M. Krisch, and C. Thomsen
Phys. Rev. B 76, 035439 (2007)
10. Raman spectroscopy of pentyl-functionalized carbon nanotubes
M. Müller, J. Maultzsch, D. Wunderlich, A. Hirsch, and C. Thomsen
phys. stat. sol. (RRL) 1, No 4, 144-146 (2007)
92
11.
Dependence of the Raman Spectrum of Silicon Nanowires on the Wire
Environment
H. Scheel, S. Reich, and C. Thomsen
in Nanowires and Carbon Nanotubes -- Science and Applications, edited by P. Bandaru,
M. Endo, I.A.Kinloch, A.M. Rao (Mater. Res. Soc. Symp. Proc. 963E, Warrendale, PA,
2007)
12.
First and second optical transitions in single-walled carbon nanotubes: a resonant
Raman study
H. Telg, J. Maultzsch, S. Reich, and C. Thomsen
phys. stat. sol. (b) 244, 4006-4010 (2007)
13.
Detail study of the Raman-active modes in carbon nanotubes
M. Mohr, M. Machón, C. Thomsen, I. Milovsevic, and M. Damnjanovic
phys. stat. sol. (b) 244, 4275-4278 (2007)
14. Raman spectroelectrochemistry on SWNTs at higher doping levels: evidence for a
transition to intercalative doping
P. M. Rafailov, C. Thomsen, U. Dettlaf-Weglikowska, B. Hornbostel, and S. Roth
phys. stat. sol. (b) 244, 4060-4063 (2007)
15. * Raman spectroscopy on chemically functionalized carbon nanotubes
M. Müller, J. Maultzsch, D. Wunderlich, A. Hirsch, and C. Thomsen\\
phys. stat. sol. (b) 244, 4056-4059 (2007)
16.
Resonant Raman scattering at exciton intermediate states in ZnO
M.R. Wagner, P. Zimmer, A. Hoffmann, and C. Thomsen
phys. stat. sol. (RRL) 1, No. 5, 169-171 (2007)
17.
Effect of ZnS shell on the Raman spectra from CdSe nanorods
H. Lange, M. Machón, M. Artemyev, U. Woggon, and C. Thomsen
phys. stat. sol. (RRL) 1, No. 6, 274-276 (2007)
18. * Vibrational properties of semitrimer picotubes
N. Rosenkranz, M. Machón, R. Herges, and C. Thomsen
Chem. Phys. Lett. 451, 249 (2008)
19. * High Levels of Electrochemical Doping of Carbon Nanotubes: Evidence for a
Transition from Double-Layer Charging to Intercalation and Functionalization
P. M. Rafailov, C. Thomsen, U. Dettlaff-Weglikowska, and S. Roth
J. Phys. Chem. B 112, 5368 (2008)
20.
Carbon-nanotube bloch equations: A many body approach to nonlinear and
ultrafast optical properties
M. Hirtschulz, F. Milde, E. Malic, S. Butscher, C. Thomsen, S. Reich, and A. Knorr
Phys. Rev. B 77, 035403 (2008)
93
21.
Zn interstitial related donors in ammonia-treated ZnO powders
J. Sann, J. Stehr, A. Hofstaetter, D.M. Hofmann, A. Neumann, M. Lerch, U. Haboeck,
A. Hoffmann, and C. Thomsen
Phys. Rev. B 76, 195203 (2007)
22.
Preface: Electronic Properties of Novel Nanostructures
Hans Kuzmany, Peter Dinse, Siegmar Roth, Christian Thomsen
phys. stat. sol. (b) 244, Issue 11, 3841-3844 (2007)
23.
Special issue: Electronic Properties of Novel Nanostructures
Hans Kuzmany, Peter Dinse, Siegmar Roth, Christian Thomsen
24. * Experimental investigation of exciton-LO-phonon couplings in CdSe/ZnS core/shell
nanorods
H. Lange, M. Artemyev, U. Woggon, T. Niermann, and C. Thomsen
Phys. Rev B. 77, 193303 (2008)
25.
G- and G+ in the Raman spectrum of isolated nanotube: a study on resonance
conditions and lineshape
H. Telg, M. Fouquet, J. Maultzsch, Y. Wu, B. Chandra, J. Hone, T. F. Heinz, C.
Thomsen
26. * Silicon nanowire optical Raman line shapes at cryogenic and elevated
temperatures
H. Scheel, S. Khachadorian, M. Cantoro, A. Colli, A. C. Ferrari, C. Thomsen
27.
Carbon nanotubes for interconnects in VLSI integrated circuits
J. Robertson, G. Zhong, H. Telg, C. Thomsen, J. M. Warner, G. A. D. Briggs,
U. Detlaff, S. Roth, J. Dijon
28.
Electrochemical functionalization of SWNT bundles in acid and salt media as
observed by Raman and X-ray photoelectron spectroscopy
Peter M. Rafailov, Christian Thomsen, Milko Monev, Urszula Dettlaff-Weglikowska,
Siegmar Roth
29.
Theory of ultrafast intraband relaxation in carbon nanotubes
Matthias Hirtschulz, Frank Milde, Ermin Malic, Christian Thomsen, Stephanie Reich,
Andreas Knorr
30.
Diameter dependence of addition reactions to carbon nanotubes
M. Müller, J. Maultzsch, D. Wunderlich, A. Hirsch, C. Thomsen
94
31.
Effects of a ZnS-shell on the structural and electronic properties of CdSe-nanorods
M. Mohr, C. Thomsen
32.
Vibrational properties of four consecutive carbon picotubes
Nils Rosenkranz, María Machón, Rainer Herges, Christian Thomsen
33.
Raman excitation profiles of β-carotene - novel insights into the nature of the ν1band
Norman Tschirner, Matthias Schenderlein, Katharina Brose, Eberhard Schlodder, Maria
Andrea Mroginski, Peter Hildebrandt, Christian Thomsen
34.
Preface: Electronic Properties of Novel Nanostructures
Christian Thomsen, Peter Dinse, Hans Kuzmany, Siegmar Roth,
35. * Growth and characterisation of high-density mats of single-walled carbon
nanotubes for interconnects
J. Robertson, G. Zhong, H. Telg, C. Thomsen, J. H. Warner, G. A. D. Briggs, U.
Detlaff-Weglikoswka, S. Roth
Appl. Phys. Lett., 93, 163111 (2008)
36. * Direct observation of the radial breathing mode in CdSe nanorods
Holger Lange, Marcel Mohr, Christian Thomsen, Mikhail Artemyev, Ulrike Woggon
Nanoletters 8, 4614-4617 (2008)
37.
Analysis of multiwalled carbon nanotubes as waveguides and antennas in the
infrared and the visible regimes
M. V. Shuba, G. Ya.Slepyan, S. A. Maksimenko, C. Thomsen, A. Lakhtakia
submitted (06/08)
38.
Carbon nanotube as a nanoscale Cherenkov-type light emitter -- nanoFEL
K. G. Batrakov, S.A. Maksimenko, P.P. Kuzhir, C. Thomsen
submitted (08/08)
39. * Phonons in bulk CdSe and CdSe nanowires
M. Mohr, C. Thomsen
Nanotechnology, in print (2009)
40.
The ground state in hydrogen passivated Si nanowire reconstructions
H. Scheel, S. Reich, C. Thomsen
submitted (10/08)
41.
Geometry dependence of the phonon modes in CdSe nanorods
Holger Lange, Mikhail Artemyev, Ulrike Woggon, Christian Thomsen
Nanotechnology 20, 045705 (2009)
95
42. * Longitudinal optical phonons in metallic and semiconducting carbon nanotubes
M. Fouquet, H. Telg, J. Maultzsch, Y. Wu, B. Chandra, J. Hone, T. F. Heinz, and C.
Thomsen
Phys. Rev. Lett., in print (2009)
43.
Chemical vapor deposition of carbon layers on Si001 substrates
T.I. Milenov, P.M. Rafailov, G.V. Avdeev, C. Thomsen
J. Optoelectronics and Advanced Materials xxx, yyy (2009)
44.
Spectroscopic studies on electrochemically doped and functionalized singel-walled
carbon nanotubes
P. M. Rafailov, T. I. Milenov, M. Monev, G. V. Avdeev, C. Thomsen, U. DettlaffWeglikowska, S. Roth
J. Optoelectronics and Advanced Materials xxx, yyy (2009)
45. * Raman spectra and DFT calculations of the vibrational modes of hexahelicene
C. Thomsen, M. Machón, and S. Bahrs
Chemical Physics Letters, submitted (2008)
46. * Vibrational properties of graphene nanoribbons by first-principles calculations
Roland Gillen, Marcel Mohr, Janina Maultzsch, Christian Thomsen
Phys. Rev. B, submitted (2009)
47. * Raman spectra of β-carotene
N. Tschirner
in preparation
96
97
9.2a.3 Invited talks
Christian Thomsen
Von eLearning bis eResearch: Virtuelle Labore & RmoteExperimente in den Naturwissenschaften
Grundfragen Multimedialen Lehrens und Lernens, GML2, Berlin,
Germany, March 2007
Janina Maultzsch
Fano Lineshape in the high-energy Raman modes of isolated
metallic carbon nanotubes
21th International Winterschool/Euroconference on Electronic
Properties of Novel Materials, Electronic Properties of Novel
Nanostructures, Kirchberg, Austria, March 2007
Sevak Khachadorian
Remote experiments
eLearning with remote experiments, Isfahan, Iran, March 2007
Christian Thomsen
Raman scattering in carbon nanotubes
Workshop on Nanotubes, Zürich, Switzerland, May 2007
Christian Thomsen
Vibrational Spectroscopy of Carbon Nanotubes
106the Bunsentagung, Graz, Austria, May 2007
Janina Maultzsch
Electron-phonon coupling in metallic carbon nanotubes observed
by Raman scattering
E-MRS Spring Meeting 2007 (European Materials Research Society,
Strasbourg, France, May 2007
Christian Thomsen
Rabi oscillations in a quantum dot exposed to quantum light
E-MRS Spring Meeting 2007, Strasbourg, France, June 2007
Christian Thomsen
Raman spectroskopy of carbon nanotubes
2nd International Workshop on Nanotube Optics &
Nanospectroscopy, Wonton 2007, Ottawa, Canada, June 2007
Christian Thomsen
Raman spectroscopy of carbon nanotubes
57. Jahrestagung der Österreichischen Physikalischen Gesellschaft,
Krems, Austria, September 2007
Janina Maultzsch
Tutorial on Micro and Nano-Raman spectroscopy
First International Conference on Micro/Nano-Reliability , Berlin,
Germany, September 2007
Janina Maultzsch
Electron-phonon coupling in metallic carbon nanotubes observed
by Raman scattering
XVII Symposium on Condensed Matter Physics, Vrsac, Serbia,
September 2007
Christian Thomsen
Optische Eigenschaften von Kohlenstoffnanoröhren
Workshop: Moderne Nanomaterialien, Greifswald, Germany,
October 2007
98
Holger Lange
Interface phonons in CdSe/ZnS core/shell-nanorods
DPG Frühjahrstagung 2008 , Berlin, Germany, February 2008
Sevak Khachadorian
Rotverschiebung der Ramanpeaks von SiNWs:thermische Einflüsse
Marcel Mohr
First principles calculations of CdSe nanowires
Christian Thomsen
Optische Eigenschaften von Kohlenstoffnanoröhren
Nanomaterialien, Braunschweig, Germany, May 2008
Marcel Mohr
First-principles calculations of CdSe nanowires
Nanomaterials, Belgrad, Serbia, June 2008
Hagen Telg
Raman Spectroscopy on single walled carbon nanotubes
Nanosystems and -materials, Rehovot, Israel/ Weizmann Institute of
Science, Rehovot, Israel, June 2008
Christian Thomsen
Raman Spectroscopy of Nanotubes and Nanorods
NT 08 (Nanotubes 2008), Montpellier, France, July 2008
Janina Maultsch
Vibrational Properties of graphene and graphene nanoribbons
Graphene Rundgespräch, Banz, Germany, September 2008
Holger Lange
Raman scattering study of CdSe nanorods
E-MRS Fall Meeting 2008, Poland, September 2008
Matthias Müller
Resonant Raman Scattering on Chemically Functionalized
Carbon Nanotubes
Raman Spetroscopy in Nanomaterials, Jülich, Germany, November
2008
99
9.2a.4 PhD theses
Harald Scheel
Silicon Nanowire Properties from Theory and Experiment
10.09.2007
Roodenko, Ecatherina Surface and interface structure of electrochemically grafted
ultra- thin organic films on metallic and semiconducting
materials
14.12.2007
Gründer, Yvonne
X-ray in-situ study of copper electrodesposition on UHV
preparedGaAs(001) surfaces
02.06.2008
Anhalt, Klaus
Radio metric measurement of thermodynamic temperatures
during the phase transformation of metal-carbon eutectic alloys
for a new high-temperature scale above 1000° C
25.07.2008
9.2a.5 Diploma theses
Polte, Jörg
One-dimensional Arrangement of endohedral Fullerences
24.05.2007
Bügler, Max
Untersuchungen des optischen Gewinns in Gruppe-III Nitriden
14.06.2007
Fouquet, Martin
Resonant Raman Spetroscopy in isolated singlewalled carbon
nanotubes
10.09.2007
Rosenkranz, Nils
Vibrational properties of carbon picotubes: experiment and
theory
08.10.2007
Khachadorian, Sevak
Thermische Effekte in Sizilium Nanondrähten
23.10.2007
Nisse, Carola
Ramanresonanzen defektinduzierter Moden in GdBa2Cu3O7-O
und (Y/Pr) Ba2 Cu3O7-O
15.11.2007
Kreutzer, Martin
Wechselwirkung zwischen Glutamat und Polypyrrol
21.12.2007
Kirste, Ronny
Ramanspektroskopie an Gruppe-III-Nitriden
03.01.2008
100
Eckhard, David
Untersuchungen der indirekten Lumineszenz in
selbstorganisierten InAs/GaAs-Quantenpunkten unter hohem
hydrostatischen Druck
22.01.2008
Werner, Stefan
Exziton-Phonon Wechselwirkung in InAs Quantenpunkten
18.02.2008
Brose, Katharina
Ramanstreuung an Biomolekülen
07.04.2008
Houpt, Lars
Neue elektromagnetische Untersuchungen zur norddeutschen
Leitfähigkeitsanomalie
14.05.2008
101
9.2a.6 Abstracts of selected papers of department IIa
Europhysics Letters77 37003 (2007)
2.
Evidence of breakdown of the spin symmetry in diluted 2D electron gases
P. Giudici1, A. R. Goni2, P. G. Bolcatto3, C. R. Proetto4, C. Thomsen1,
K. Eberl5 and M. Hauser5
1
Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623
Berlin, Germany
2
ICREA Research Professor, Institut de Ciència de Materials de Barcelona, Campus de la
UAB - 08193 Bellaterra, Spain
3
Facultad de Ingeniería Química and Facultad de Humanidades y Ciencias, Universidad
Nacional del Litoral – 3000 Santa Fe, Argentina
4
Centro Atómico Bariloche and Instituto Balseiro - 8400 S. C. de Bariloche, Río Negro,
Argentina
5
MPI für Festkörperforschung - Heisenbergstr. 1, 70569 Stuttgart, Germany
Abstract – Direct evidence of spin polarisation in dilute two-dimensional electron gases
formed in modulation-doped single quantum wells has been obtained from resonant inelastic
light scattering. The abrupt enhancement of the exchange-correlation energy of collective
intersubband spin and charge excitations observed at very low occupations of the second
subband is the signature of the breakdown of the spin symmetry. Calculations of the
elementary excitations within the timedependent local spin-density approximation provide an
explanation for the striking behaviour of the different terms of the Coulomb interaction and
predict the existence of a ferromagnetic ground state in the very diluted regime.
102
THE JOURNAL OF CHEMICAL PHYSICS 126, 124701 (2007)
3.
Dynamics of magnetic-field-induced clustering in ionic ferrofluids
from Raman scattering
D. Heinrich1, C. Thomsen1, A. R. Goñi2
1
Berlin, Germany
2
ICREA, Institut de Ciència de Materials de Barcelona, Campus de la UAB, 08193
Bellaterra, Spain
Using Raman spectroscopy, the authors have investigated the aggregation/disgregation of
magnetic nanoparticles in dense ionic ferrofluids _IFF_ into clusters due to the action of an
inhomogeneous external magnetic field. Evidence for changes in particle density and/or
effective cluster size were obtained from the variation of the Raman intensity in a time
window from 10 s to 10 min for magnetic fields up to 350 mT and at a temperature of 28 °C.
Clustering sets in already at very low fields __15 mT_ and the IFF samples exhibit a clear
hysteresis in the Raman spectra after releasing the magnetic field, which lasts for many hours
at room temperature. The authors determined the characteristic times of the two competing
processes, that of field-induced cluster formation and, at room temperature, that of thermalactivated dissociation, to range from 100 to 150 s.
4.
Hierold, WILEY-VCH, Weinheim, 2008 ISBN: 978-3-527-31720-2 (2008)
Characterization of Carbon Nanotubes by Optical Spectroscopy
Janina Maultzsch and Christian Thomsen
Hardenbergstraße 36, 10623 Berlin, Germany
Characterization of carbon nanotubes for applications in electronic, nanomechanical or
sensing devices can be performed by various methods including optical spectroscopy,
scanning probe techniques or electron diffraction. The method of choice depends on the
required level of characterization, for instance whether it is sufficient to distinguish metallic
from semiconducting nanotubes or whether the chiral index must be determined. Furthermore,
it depends on the sample conditions such as its environment, and whether one is interested in
a single nanotube or in nanotube ensembles. For example, an individual nanotube as part of a
single-molecule electronic devicemight need to be characterized. On the other hand, after
nanotube synthesis large quantities of nanotubes might require analysis regarding their
diameter and purity, or chemical treatment of nanotube suspensions is to be monitored.
Optical spectroscopy is a versatile, non-destructive method which can be applied under many
different conditions and which ranges from detecting the presence of carbon nanotubes to
identifying the chiral index (n,m). Here we give a review on how to use optical spectroscopy
for characterizing carbon nanotubes.
103
Phys. Rev. B 75, 153408 (2007)
7.
Elasticity of single-crystalline graphite: Inelastic x-ray scattering study
Alexey Bosak2, Michael Krisch2, Marcel Mohr1, Janina Maultzsch1, and Christian Thomsen1
1
2
Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36,
10623 Berlin, Germany
European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
The five independent elastic moduli of single-crystalline graphite are determined using
inelastic x-ray scattering. At room temperature the elastic moduli are, in units of GPa,
C11=1109, C12=139, C13=0, C33=38.7 and C44=4.95. Our experimental results are compared
with predictions of ab initio calculations and previously reported incomplete and
contradictory data sets. We obtain an upper limit of 1.1 TPa for the on-axis Young’s modulus
of homogeneous carbon nanotube, thus providing important constraints for further theoretical
advancesand quantitative input to model elasticity in graphite nanotubes.
Phys. Rev. B. 75, 195401(2007)
8.
Mixing of the fully symmetric vibrational modes in carbon nanotubes
M. Mohr1, M. Machón1, C. Thomsen1, I. Milošević2 and M. Damnjanović2
1
2
Faculty of Physics, University of Belgrade, P.O. Box 368, 11011 Belgrade, Serbia
We study the mixing of the fully symmetric modes in single-walled carbon nanotubes with ab
initio calculations. With a variational model, we confirm the results from finite-difference
calculations. We further analyze the effect of the mixing on the calculation of phonon
frequencies and electron-phonon coupling matrix elementsMe-ph. We find that neglecting the
mixing leads to errors of up to 60% forMe-ph for the radial breathing mode and up to 50 cm−1
difference for the high-energy mode frequency.
104
Phys. Rev. B 76, 035439 (2007)
9.
The Phonon dispersion of graphite by inelastic x-ray scattering
M. Mohr1, J. Maultzsch1, E. Dobardžić 2 , S. Reich3 , I. Milošević2, M. Damnjanović2,
A. Bosak4, M. Krisch4 and C. Thomsen1
1
2
3
Faculty of Physics, University of Belgrade, POB 368, 11011 Belgrade, Serbia
Department of Materials Science and Engineering, Massachusetts Institute of Technology,
77 Massachusetts Avenue,Cambridge, Massachusetts 02139-4307, USA
4
European Synchrotron Radiation Facility (ESRF), BP 220, F-38043 Grenoble Cedex,
France
We present the full in-plane phonon dispersion of graphite obtained from inelastic x-ray
scattering, including the optical and acoustic branches, as well as the midfrequency range
between the K and M points in the Brillouin zone, where the experimental data have been
unavailable so far. The existence of a Kohn anomaly at the K point is further supported. We
fit a fifth-nearest neighbor force-constant model to the experimental data, making improved
force-constant calculations of the phonon dispersion in both graphite and carbon nanotubes
available.
phys. stat. sol. (b) 244, No. 11, 4056–4059 (2007)
15.
Raman spectroscopy on chemically functionalized carbon nanotubes
M. Müller1, J. Maultzsch2, D. Wunderlich3, 4, A. Hirsch3, 4 and C. Thomsen1
1
Berlin, Germany
2
Departments of Electrical Engineering and Physics, Columbia University, New York, NY
10027, USA
3
Zentralinstitut für Neue Materialien und Prozeßtechnik, Universität Erlangen-Nürnberg,
Dr.-Mack-Str. 81, 90762 Fürth, Germany
4
Institut für Organische Chemie, Universität Erlangen-Nürnberg, Henkestr. 42, 91054
Erlangen,Germany
We present Raman spectroscopy on carbon nanotubes, functionalized with alkyl groups to
different degrees and with different addition reactions. We observe effects in particular on the
intensities of the radial breathing mode (RBM). From the RBM we can assign the diameter
and chiral indices of the tubes and study the influence of functionalization on different tubes,
their transition energies, Raman shifts and RBM intensities.We observe a diameter
dependence of the chemical reaction under certain reaction conditions.
105
18.
Chemical Physics Letters 451, 249251 (2008)
Vibrational properties of semitrimer picotubes
N. Rosenkranz1, M. Machón1, R. Herges2 and C. Thomsen1
1
2
Institut für Organische Chemie, Christian-Albrechts-Universität Kiel,
Otto-Hahn-Platz 4, 24098 Kiel, Germany
The semitrimer picotube is a ring-shaped hydrocarbon closely related to a very short (3,3)
carbon nanotube. We study the vibrational properties of the semitrimer by means of Raman
spectroscopy and find the structural similarity to nanotubes to be reflected also in the
vibrational spectra. In particular, combining polarization-dependent Raman measurements
and ab inito calculations we can identify a fully symmetric vibration corresponding to
theradial breathing mode in nanotubes.
19.
J. Phys. Chem. B 112, 5368-5373(2008)
High Levels of Electrochemical Doping of Carbon Nanotubes: Evidence for
a Transition from Double-Layer Charging to Intercalation and
Functionalization
Peter M. Rafailov1, Christian Thomsen2, Urszula Dettlaff-Weglikowsk1 and Siegmar Roth3
1
Georgi NadjakoV Institute of Solid State Physics, Bulgarian Academy of Sciences, 72
Tzarigradsko Chaussee BlVd., 1784 Sofia, Bulgaria
2
Institut für Festkörperphysik, Technische Universität Berlin
3
Max-Planck-Institut für Festkörperforschung,
Heisenbergstrasse 1, 70569 Stuttgart, Germany
We studied the transition from the electrochemical double-layer charging regime to
intercalative doping of bundled single-walled carbon nanotubes (SWNT) in KCl and HCl
aqueous solution. For this purpose we used high doping levels by applying constant potentials
above 1000 mV approaching and slightly exceeding the oxidation potential for Cl- ions. At
each potential in situ Raman measurements of the radial breathing mode (RBM), the highenergy tangential mode (HEM), and the disorder-induced (D) mode were performed.
Furthermore, the conductivity and reflectivity of a set of SWNT samples were measured as a
function of doping and subsequently the samples were examined by X-ray photoelectron
spectroscopy (XPS). From a comparative analysis of the results we conclude that above 1000
mV a significant penetration of chlorine species into the interstitial channels of the SWNT
bundles and possible covalent functionalization take place.
106
24.
PHYSICAL REVIEW B 77, 193303 (2008)
Experimental investigation of exciton-LO-phonon couplings in CdSe/ZnS
core/shell nanorods
Holger Lange1, Mikhail Artemyev2, Ulrike Woggon3,
Tore Niermann4 and Christian Thomsen1
1
Berlin, Germany
2
Institute for Physico-Chemical Problems, Belarusian State University, 14 Leningradskaya
Str., Minsk 220080, Belarus
3
Fachbereich Physik, Universität Dortmund, Otto-Hahn-Str. 4, 44227 Dortmund, Germany
4
Institut für Optik und Atomare Physik, Technische Universität Berlin, Straße des 17. Juni
135, 10623 Berlin, Germany
We investigate the size dependence of the exciton-LO-phonon coupling strength in colloidal
CdSe nanorods coated with an epitaxial ZnS shell. We find an increase in the coupling
strength with decreasing nanorod diameter. The growth of a ZnS shell on the nanorod surface
much more strongly reduces the exciton-phonon coupling strength than expected from
geometry considerations. The determined radius dependence of the Huang-Rhys factor is
similar to that observed for spherical CdSe nanocrystals.
26.
phys. stat. sol. (b) 245, No. 10, 2090–2093 (2008)
Silicon nanowire optical Raman line shapes at cryogenic and elevated
temperatures
H. Scheel1, S. Khachadorian1, M. Cantoro2, A. Colli2, A. C. Ferrari2 and C. Thomsen1
1
Institut für Festkörperphysik, Technische Universität Berlin, Berlin, Germany
2
Department of Engineering, University of Cambridge, Cambridge CB3 OFA, UK
We report the Raman spectra of silicon nanowires (SiNWs) in a wide temperature range,
between 2 K and 850 K. At room temperature we find a strong influence on the spectrum
from applied laser excitation powers. These effects can be attributed a laser heated sample,
leading to an inhomogeneous temperature distribution within the laser-spot. If the laser
excitation power is small (below 100 μW) such effects are negligible, and we find a
temperature dependence governed by threephonon decay processes. The results from
temperature dependent measurements indicate a change of sample morphology due to heating.
Raman measurements on SiNWs immersed in superfluid helium at ≈ 2 K show very strong
red-shifts, even though they still have the perfect thermal contact via the superfluid helium.
Considering anharmonic effects we find massively increased Si core temperatures.
107
35.
APPLIED PHYSICS LETTERS 93, 163111 (2008)
Growth and characterization of high-density mats of single-walled carbon
nanotubes for interconnects
J. Robertson1, G. Zhong1, H. Telg2, C. Thomsen2, J. H. Warner3, G. A. D. Briggs3,
U. Dettlaff-Weglikowska4 and S. Roth4
1
Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United
Kingdom
2
3
Department of Materials, University of Oxford, Oxford OX1 3PH, United Kingdom
4
Max Planck Institut für Festkörperphysik, D-70569 Stuttgart, Germany
We grow high-density, aligned single wall carbon nanotube mats for use as interconnects in
integrated circuits by remote plasma chemical vapor deposition from a Fe–Al2O3 thin film
catalyst.We carry out extensive Raman characterization of the resulting mats, and find that
this catalyst system gives rise to a broad range of nanotube diameters, with no preferential
selectivity of semiconducting tubes, but with at least 13 of metallic tubes.
36.
Nano Lett., 8 (12), 4614-4617 (2008)
Direct Observation of the Radial Breathing Mode in CdSe Nanorods
Holger Lange1, Marcel Mohr1, Mikhail Artemyev2, Ulrike Woggon3, and Christian Thomsen1
1
Institut für Festkörperphysik, Technische Universität Berlin, Germany
2
Institute forPhysico-Chemical Problems of Belorussian State University, Minsk, Belarus
3
Institut für Optik und Atomare Physik, Technische Universität Berlin, Germany
We experimentally confirm the existence of the radial breathing mode in CdSe nanorods by
Raman spectroscopy, which was deduced from ab initio calculations of the vibrational
properties of bare CdSe nanowires and CdSe/ZnS core-shell nanowires. We calculated the
modes’frequency for various diameters and measured a set of bare CdSe nanorods and
CdSe/ZnS core-shell nanorods to determine the diameter dependence of the modes’
frequency. The frequency of this mode is strongly diameter dependent and it can be used to
estimate the nanorod diameter from a Raman measurement alone.
108
39.
Nanotechnology, in print (2009)
Phonons in bulk CdSe and CdSe nanowires
Marcel Mohr and Christian Thomsen
We present first-principles calculations on bulk CdSe and CdSe nanowires with diameters of
up to 22\,\AA. Their electronic and structural properties are presented and discussed. The
vibrational properties of bulk CdSe and the zone-center vibrations of the nanowires are
calculated and analyzed. An iterative, symmetry-based relaxation method is used that yields
improved results for phonon frequencies.We find that the band gap varies with the surface
termination and that strongly size-dependent and nearly constant vibrational modes exist in
the nanowires, depending on the displacement directions. A strong shift in frequency for
specific modes is found, stemming from surface contributions to the polarization, similar to
that reported for thin slabs. A comparison with experimental data from Raman measurements
is given.
42.
Physical Review Letters, in print (2009)
Longitudinal optical phonons in metallic and semiconducting carbon
nanotubes
Martin Fouquet1, Hagen Telg1, Janina Maultzsch1, 2, Yang Wu2, Bhupesh Chandra3, J. Hone3,
Tony F. Heinz2 and Christian Thomsen1
1
2
Departments of Electrical Engineering and Physics, Columbia University,
New York 10027 USA
3
Department of Mechanical Engineering, Columbia University, New York 10027 USA
We analyze the high-energy Raman modes, G+ and G-, in a pair of one metallic and one
semiconducting nanotube. By combining Rayleigh scattering with Raman resonance profiles
of the radial breathing mode and the high-energy modes, we show that the observed G- and G+
peaks can originate from longitudinal optical phonons of different tubes. The G- peak is the
longitudinal mode of the metallic tube; it is broadened and downshifted due to strong
electron-phonon coupling in the metallic nanotube. The G+ peak is due to the longitudinal
mode in the semiconducting tube. This result resolves an ongoing debate in the literature.
109
45.
Chemical Physics Letters, submitted (2008)
Raman spectra and DFT calculations of the vibrational modes of
hexahelicene
C. Thomsen, M. Machón, and S. Bahrs
We performed Raman spectra of the polycyclic aromatic molecule hexahelicene and
compared the about 50 identified vibrational modes with those of coronene. Hexahelicene has
a similar structure as coronene but lower symmetry due to a cut of the molecule in radial
direction. Correspondingly, there are many more modes in the spectra. We calculated the
eigenfrequencies and eigenvectors of both molecules with ab-initio- methods and compared
experiment and calculation, together with an assignment of the vibrational modes of
hexahelicene.
46.
Phys. Rev. B, submitted (2009)
Vibrational properties of graphene nanoribbons by first-principles
calculations
Roland Gillen, Marcel Mohr, Janina Maultzsch and Christian Thomsen
Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin
We investigated the vibrational properties of graphene nanoribbons by means of firstprinciples calculations on the basis of density functional theory. We confirm that the phonon
modes of graphene nanoribbons with armchair and zigzag type edges can be interpreted as
fundamental oscillations and overtones. These show a characteristic dependence on the
nanoribbon width. Furthermore, we demonstrate that a mapping of the calculated Γ-point
phonon frequencies of nanoribbons onto the phonon dispersion of graphene corresponds to an
“unfolding” of nanoribbons onto graphene. We consider the influence of spin states with
respect to the phonon spectra of zigzag nanoribbons and provide comparisons of our results
with past studies.
47.
in preparation (2009)
Raman spectra of β-carotene
Norman Tschirner, Peter Hildebrandt and Christian Thomsen
In the present work we have studied β-carotene dissolved in dichloromethane by means of
resonance Raman spectroscopy. To obtain the Raman excitation profiles Raman spectra of
carotene have been acquired at various wavelengths throughout the visible region. It was
found that the position of the prominent peak at ca. 1524 cm-1 varies with the excitation
wavelength indicating the involvement of two different modes. Possible origins of the
different enhancement pattern of the two modes are discussed.
110
111
9.2.b Department IIb
Prof. em. Dr.-Ing. Dr. h.c. mult. Immanuel Broser
9.2b.0 Staff
Secretary
Kathrin Haberland (part time)
Senior scientists
Dr. Til Bartel (until 28.02 2008)
Dr. Matthias Dworzak (until 31.03.2007)
Dr. Enno Malguth (until 30.06.2008)
PhD candidates (status of 31.12.2008: thesis completed = c)
Dipl.-Phys. Max Bügler
Dipl.-Phys. Munise Cobet
Dipl.-Phys. Ute Haboeck
Dipl.-Phys. Ronny Kirste
Dipl.-Phys. Christian Kindl
Dipl.-Phys. Tobias Schulze
Dipl.-Phys. Markus Wagner
Dipl.-Phys. Stefan Werner
Dipl.-Phys. Patrick Zimmer
Diploma students (status of 31.12.2008: thesis completed = c)
Miran Alic
Max Bügler (c)
Gordon Callson
Ole Hitzmann
Martin Kaiser
Ronny Kirste (c)
Christian Nenstiel
Christian Rauch (c)
Jan Hindrik Schulze
Stefan Werner (c)
Thomas Switaiski
112
113
9.2b.1 Summary of activities
The main research activities concentrate on the optical properties of wide-band gap II-VI and
III-V semiconductors with special emphasis on ZnO- and GaN-based structures. The
investigations are carried out on single crystals, epitaxially grown heterostructures and,
especially, low-dimensional structures like quantum wells and quantum dots.
In the last years new activities were started like studies of the magneto-optical investigations
for spintronic application, investigations of the energy transfer in organic light-emitting
diodes and non-linear optics in chalcopyrites. Cooperations have been established with many
research groups in Germany, France, Russia, Belarus, United Kingdom, USA and Japan. The
essential physical topics include:
excitonic polaritons and bound excitons in bulk crystals and excitonic complexes
in low dimensional structures based on InGaN, AlGaN, InGaAs and InGaAsN,
shallow and deep centers,
recombination dynamics and non-radiative processes,
non-linear optical effects of pure and doped wide-gap semiconductors,
coherent dynamics,
optical gain mechanisms,
analysis of doping and dopant compensation mechanisms, and
electro-optical effects in polymers.
Excitonic complexes, their excitation and relaxation mechanisms and the dynamics of these
processes are in our center of interest. Knowledge about the energetic structure and relaxation
mechanisms of free and bound excitons allows a precise analysis of defects created during
growth and doping procedures. These investigations are carried out in close cooperation with
other groups aiming for the development and optimization of new optoelectronic devices like
blue light-emitting diodes and lasers. Both wide-gap II-VI and III-V semiconductors are
studied.
Our work on binary and ternary group-III nitrides has been concentrated to the experimental
determination of basic band structure parameters of this as yet poorly known material.
Many papers of the last two years have led to a complete understanding of the measured
optical properties. Also, gain mechanisms in epitaxial group-III nitride layers and quantum
wells were studied. All these investigations are of great interest for the development of blue
emitting semiconductor laser diodes.
For AlGaN- and ZnO-based structures the problem of p-dopant compensation attracts a lot of
interest. Intensive studies were dedicated to the behavior of donor-acceptor pair emissions of
highly doped ZnO-layers. Our observation, that the broad luminescence band usually
observed in highly doped material becomes much sharper at higher excitation levels, finally
turning into the normal, low doping spectrum has triggered intensive investigations using
optical spectroscopy as a function of intensity and temperature.
Currently, two different models for this effect are discussed, in highly compensated
specimens the formation of high electric fields or the existence of an exponentially
structured continuum of low lying donors or acceptors. Calculations have been performed to
distinguish between the two different methods.
The study of coherent processes especially at localized excitations is a further issue in our
research. Coherent lifetimes react very sensitively to defect structures and can thus help to
optimize growth techniques for blue light-emitting devices. Four-wave mixing techniques
could be applied to epitaxial layers of different II-VI compounds to receive non-linear
quantum beats. We have shown that they originate either from zero-field split excited states of
one complex or from interference between two different bound excitons. Coherent lifetimes
of some hundred fs were observed.
114
The purpose of the Sfb 787 project headed by Axel Hoffmann and Christian Thomsen is to
study the influence of the electron-phonon interaction in low-dimensional semiconductor
systems. Here, our main focus is the investigation of the dynamical properties of excitonic
states in II-VI and III-V quantum dots.
In cooperation with the Siemens AG experiments to measure the electro-optical coefficients
of polymers and the electro-optical properties of organic light-emitting diodes and bio-chip
readers were continued. The results are important to create new optical communication and
signal processing systems on the basis of organic materials.
115
9.2b.2 Publications
1.
Group I elements in ZnO
B.K. Meyer, N. Volbers, A. Zeuner, S. Lautenschläger, J. Sann, A.Hoffmann,
U. Haboeck
Mater. Res. Soc. Symp. Proc. Vol. 891 (2007) 0891-EE10-24.1
2.*
Polarized emission lines from A- and B-type excitonic complexes in single
InGaN/GaN quantum dots
M. Winkelnkemper, R. Seguin, S. Rodt, A. Schliewa, L. Reißmann, A. Strittmatter, A.
Hoffmann, D. Bimberg
J. Appl. Phys. 101 (2007), 113708
3.
Properties of InN layers grown by high pressure chemical vapour deposition
M. Alevli, G. Durkaya, R. Kirste, A. Weesekara, W. E. Fenwick, V. T. Woods, I.T.
Ferguson, A. Hoffmann, A.G. Perera and N. Dietz
Mat. Res. Soc. Symp. Proc. 955; Symposium I: Advances in III-V Nitride
Semiconductor, Materials and Devices, Boston, MA, USA, Nov.-Dec. 2006, I8.4, pp. 16, (2007).
4.*
On the Origin of the unexpected annealing behavior of GaInNAs quantum wells
M. Dworzak, R. Hildebrant, A. Hoffmann, L. Geelhaar, M. Galluppi, H. Riechert,
T. Remmle, M. Albrecht
Jap. J. Appl. Phys. 46 (2007), L 614
5.
Gain mechanisms in field-free InGaN layers grown on sapphire and bulk GaN
substrate
M. Dworzak, T. Stempel Pereira, M. Bügler, A. Hoffmann, G. Franssen, S. Grzanka,
T. Suski, R. Czernecki, M. Leszczynski, I. Grzegory
phys. stat. sol. (RRL) 1, 141– 143 (2007) / DOI 10.1002/pssr.200701037
6.
Photonic properties of ZnO epilayer
M.R. Wagner, U. Haboeck, P. Zimmer, A. Hoffmann, S. Lautenschläger, C. Neumann,
J. Sann, B.K. Meyer
Proc. SPIE 6474, 64740x (2007)
7.
Structure-property-function relationships in nanoscaled oxide sensors:
A case study based on zinc oxide.
S. Polarz, A. Roy, M. Lehmann, M. Driess, F. E. Kruis, A. Hoffmann, P. Zimmer
Advance Functional Materials 17, 1385 (2007)
8.*
Fabry-Perot effects in InGaN/GaN heterostructures on Si substrates
C. Hums, T. Finger, T. Hempel, J. Christen, A. Dadgar, A. Hoffmann, A. Krost
J. Appl. Phys. 101, 033113 (2007)
9.
Resonant Raman scattering at exciton intermediate states in ZnO
M. R. Wagner, P. Zimmer, A. Hoffmann, C. Thomsen
phys. stat. sol. (RRL) 1, 169– 171 (2007) / DOI 10.1002/pssr. 200701106
116
10.
Workshop on ZnO
Axel Hoffmann, Bruno. K. Meyer
phys.stat. sol (RRL), A 41 (2007)
11.
Phonons in sapphire Al2O3 for ZnO and GaN
H.W. Kunert, A.G.J. Machatine, A. Hoffmann, G. Kaczmarczyk, U. Haboeck, J.
Malherbe, J. Barnas, M.R. Wagner, J.D. Brink
Mat. Science and Engineering C 27, 1222 (2007)
12.
Rabi oscillations in a quantum dot exposed to quantum light
A. Magyarov, G. Ya. Slepyan, S.A. Maksimenko, A. Hoffmann
Mat. Science and Engineering C 27, 1030 (2007)
13.
Effects of time reversal symmetry on phonons in sapphire substrates for ZnO and
GaN
H.W. Kunert, A. Hoffmann, A.G.J. Machatine, J. Malherbe, J. Barnas, G.
Kaczmarczyk, U. Haboeck, R. Seguin
Superlattices and Microstructures, Volume 42, 278 (2007)
14.* Zn interstitial related donors in ammonia treated ZnO powders
J. Sann, J. Stehr, A. Hofstaetter, D. M. Hofmann, A. Neumann, M. Plana, M. Lerch
U.Haboeck, A. Hoffmann, C. Thomsen
Phys. Rev. B 76, 195203 (2007)
15.
Ionized and neutral donor bound excitons in ZnO
B.K. Meyer, J. Sann, S. Lautenschläger, M. R. Wagner, and A. Hoffmann
Phys. Rev. B 76, 184120 (2007)
16.* Microscopic theory of quantum dot interactions with quantum lights: local field
effects
G.Ya. Slepyan, A. Magyarov, S.A. Maksimenko, A. Hoffmann
Phys. Rev. B 76, 195328 (2007)
17.* Surface modification of Co-doped ZnO nanocrystals and its effects on magnetic
properties
A.S Pereira, S. Pereira, T. Trindade, A.O. Ankiewicz, M.C. Carmo, N.A. Sobolev, W.
Gehlhoff, A. Hoffmann, M. Grundmann
J. Appl. Phys. 103 07D 140 (2008)
18.
Optical properties of III-V quantum dots
Udo W. Pohl, Sven Rodt, Axel Hoffmann
Semiconductor Nanostructures, ed. D. Bimberg, Springer Verlag Berlin Heidelberg
New York 2008, ISBN 978-3-540-77898, p 269-300
19.
Polarized Emission Lines fromSingle InGaN/GaN Quantum Dots: Role of the
Valence-band Structure of WurtziteGroup-III Nitrides
M.Winkelnkemper, R. Seguin, S. Rodt, A. Schliwa, L. Reißmann, A. Strittmatter,
Physica E 40: Low-dimensional Systems and Nanostructures, (2008), 2217-2219
117
20.* Energy transfer in close packed PbS nanocrystal films
V. Rinnerbauer, H.-J. Egelhaaf, K. Hingerl, P. Zimmer, S. Werner, T. Warming, A.
Hoffmann, M. Kovalenko, W. Heiss, G. Hesser, F. Schaffler
Phys. Rev. B 77, 085322 (2008)
21.
Fe in III-V and II-VI compounds
Enno Malguth, Axel Hoffmann, Matthew Phillips
phys. stat. sol. (b) 245, 455 (2008) / DOI 10.1002/pssb.200743315
22.* Decay dynamics of neutral and charged excitonic complexes in single InAs/GaAs
quantum dots
M. Feucker, R. Seguin, S. Rodt, A. Hoffmann, D. Bimberg
Appl. Phys. Lett. 92, 063116 (2008)
23.
Origin of the broad lifetime distribution of localized excitons in InxGa1-xN/GaN
quantum dots
M. Winkelnkemper, M. Dworzak, T. P. Bartel, A. Strittmatter, A. Hoffmann,
D. Bimberg
phys. stat. sol. (b), 245 (2008), 2766
24.
Phonon interaction in InGaAs/GaAs quantum dots
S. Werner, P. Zimmer, A. Strittmatter, A. Hoffmann
Mat. Res. Soc. Symp. Proc. 1053, Warrendale,PA, USA, ISBN: 1-55899-846-2, EE0303 (2008)
25.* Mn- and Fe-doped GaN for spintronic applications
E. Malguth, A. Hoffmann, M. H. Kanes, I. T. Ferguson
Mat. Res. Soc. Symp. Proc. 1040, Warrendale,PA, USA, ISBN: 1-55899-846-2, Q06-09
(2008)
26.
Mn charge states in GaMnN as a function of Mn concentration and co-doping
E. Malguth, A. Hoffmann, W. Gehlhoff, M. H. Kanes, I. T. Ferguson
Mat. Res. Soc. Symp. Proc. 1040, Warrendale,PA, USA, ISBN: 1-55899-846-2, Q09-18
(2008)
27.
Optical and structural properties of homoepitaxial ZnO
T. P. Bartel, M. R. Wagner, U. Haboeck, A. Hoffmann, C. Neumann, S. Lautenschläger,
J. Sann, B. K. Meyer
Proc. SPIE 6895, 689502 (2008)
28. Asymmetry in the excitonic recombinations and impurity incorporation of the two
polar faces of homoepitaxially grown ZnO films
S. Lautenschlaeger, J. Sann, N. Volbers, B. K. Meyer, A. Hoffmann, U. Haboeck,
M. R. Wagner
Phys. Rev. B 77 (2008), 144188
29.* GaN/AlN quantum dots for single qubit emitters
M. Winkelnkemper, R. Seguin, S. Rodt, A. Hoffmann, D. Bimberg
JPCM 20 (2008), 454211
118
30.* Influence of substrate surface polarity on homoepitaxial growth of ZnO layers by
chemical vapour deposition
M. R. Wagner, T.P. Bartel, R. Kirste, A. Hoffmann, J. Sann, S. Lautenschläger, B. K.
Meyer, C. Kieselowski
Phys. Rev. B 79(2009), 035307
31.
Bound and free excitons in ZnO: optical selection rules in the absence and
presence of time reversal symmetry
M.R. Wagner, H.W. Kunert, A.G.J. Machatine, A. Hoffmann, P. Niyongabo, J.
Malherbe, J. Barnas
Superlattices and Microstructures, Volume xx, xxx (2009)
32.
Structural and optical inhomogeneities of Fe doped GaN grown by HVPE
E. Malguth, A. Hoffmann, M.R. Phillips
J. Appl. Phys. 104 (2008), 123712
33.
Strong coupling of light with one-dimensional quantum dot chain from Rabi
oscillations to Rabi waves
G. Ya Slepyan, Y.D. Yerchak, S.A. Maksimenko, A. Hoffmann
Phys. Rev.. B xxx (2008), xxx
34.* Field-matter strong coupling in two-level quantum systems with broken inversion
symmetry
O.V. Kibis, G. Ya Slepyan, S.A. Maksimenko, A. Hoffmann
Phys. Rev. Lett. 102 (2009), 023601
35.
Magnetic and structural properties of transition metal doped zinc-oxide
nanostructures
A.O. Ankiewicz, W. Gehlhoff, J.S. Martins, A. S. Pereira, S. Pereira, A. Hoffmann,
E. M. Kaidashev, A. Rahm, M. Lorenz, M. Grundmann, M. C. Carmo, T. Trindade,
N. A. Sobolev
phys.stat.sol. (b) 200880581(2009), 1
36.
Infrared absorption, multiphonon processes and time reversal effect on Si and Ge
band structure
H.W. Kunert, A.G.J. Machatine, J. Malherbe, J. Barnas, A. Hoffmann, M.R. Wagner
Thin Solid Films 517, 134 (2008)
37.
Elementary excitation in Si, Ge band and diamond time reversal affected
H.W. Kunert, A.G.J. Machatine, J. Malherbe, J. Barnas, A. Hoffmann, M.R. Wagner
Thin Solid Films 517, 372 (2008)
38.
Spectral identification of impurities and native defects in ZnO
B.K. Meyer, D.M. Meyer, J. Stehr, A. Hoffmann
Springer Buch über ZnO (C. Litton) 2009
39.* Nitrogen incorporation in homoepitaxial ZnO CVD epilayers
S. Lautenschlaeger, S. Eisermann, B.K. Meyer, G. Callsen, A. Hoffmann
phys. stat. sol (RRL), A 3 (2009), 16
119
40.
Effects of Li doping in ZnO nanocrystals
C. Rauch, W. Gelhoff, M.R. Wagner, E. Malguth, B. Salameh, A. Hoffmann, S. Polarz,
Y. Aksu, M. Driess
Phys. Rev. B xxx (2009), xxx
41.* Optical characterization of InN layers grown by high-pressure chemical vapour
deposition
M. Alevli, R. Ataley, G. Durkaya, A. Weesekara, G.U. Perera and N. Dietz, R. Kirste,
A. Hoffmann
J. Vac. Sci. Technol. A 26 (2008), 1023
120
121
9.2b.3 Invited talks
Axel Hoffmann
Photonic properties of ZnO
SPIE Photonic West 2007, San Jose, USA, January 2007
Axel Hoffmann
On the mechanism of Quantum dot formation in InGaN layers
grown by MOVPE
TMS Meeting Services, Las Vegas, USA, September 2007
Axel Hoffmann
Micro-Raman and resonant Raman scattering in homoepitaxialgrown ZnO
Materials Research Society (MRS), Boston, USA, November 2007
Axel Hoffmann
Mn charge states in GaMnN as a function of Mn concentration
and co-doping
Materials Research Society (MRS), Boston, USA, November 2007
Axel Hoffmann
Lattice dynamics of homoepitaxial grown ZnO
SPIE Photonic West 2008, San Jose, USA, January 2008
Axel Hoffmann
Single photon emitter for quantum-cryptography application
2nd workshop on low dimensional structures, Aveiro, Portugal,
January 2008
Axel Hoffmann
Single photon spectroscopy for quantum cryptography
application
TU Eindhoven, Netherland, March 2008
Axel Hoffmann
Single photon spectroscopy for quantum cryptography
application
University Autonoma of Barcelona, Spain, September 2008
122
123
9.2b.4 PhD theses
Anhalt, Klaus
Radiometric measurement of thermometric temperatures during
the phase transformation of metal-carbon eutectic alloys for a
new high-temperature scale above 1000 C
25.07.2008
Bartel, Til Pierre
Chemical Inhomogeneity in InxGa1-xN and ZnO - a HRTEM
Study on Atomic Scale Clustering
11.03.2008
Bügler, Max
Growth and Characterization of InN- and InGaN-layers with
high In-concentration and basic optical characterization of these
layers
07.11.2007
Dworzak, Matthias
Concepts for increasing the light efficiency in semiconductor light
emitters
11.06.2007
Johnson, Benjamin
Analysis of CU (In,Ga)S2-absorbers using XES, XPS and IPES
03.07.2007
9.2b.5 Diploma theses
Bügler, Max
Untersuchung des optischen Gewinns an Gruppe-III-Nitriden
04.05.2007
Kirste, Ronny
Ramanspektroskopie an Gruppe-III Nitriden
26.02.2008
Rauch, Christian
Magneto-Optik von Exzitonen im ZnO
27.10.2007
Werner, Stefan
Exziton-Phonon Wechselwirkung in InAs Quantenpunkten
01.03.2007
124
125
9.2b.6 Abstracts of selected papers of department IIb
2.
JOURNAL OF APPLIED PHYSICS 101, 113708 (2007)
Polarized emission lines from A- and B-type excitonic complexes
in single InGaN/GaN quantum dots
M. Winkelnkemper
Institut für Festkörperphysik, Technische Universität Berlin, D-10623 Berlin, Germany and
Fritz-Haber-Institut der Max-Planck-Gesellschaft, D-14195 Berlin, Germany
R. Seguin, S. Rodt, A. Schliwa, L. Reißmann, A. Strittmatter, A. Hoffmann,
D. Bimberg
Cathodoluminescence measurements on single InGaN/GaN quantum dots _QDs_ are
reported. Complex spectra with up to five emission lines per QD are observed. The lines are
polarized along the orthogonal crystal directions [1120] and [100]. Realistic eight-band k ·p
electronic structure calculations show that the polarization of the lines can be explained by
excitonic recombinations involving hole states which are formed either by the A or the B
valence band.
4.
JAPANESE JOURNAL OF APPLIED PHYSICS 46, L 614 (2007)
On the Origin of the Unexpected Annealing Behavior of GaInNAs
Quantum Wells
Matthias Dworzak, Radowan Hildebrandt, Axel Hoffmann, Lutz Geehaar1, Massimo
Galuppi1, Henning Riechert1, Thilo Remmele2, Martin Albrecht2
Institute of Solid State Physics, Technical University Berlin, Hardenbergstr. 36, D-10623
Berlin, Germany
1Qimonda (formerly Infineon Technologies), D-81730 Munich, Germany
2Institute of Crystal Growth, Max-Born-Str. 2, D-12489 Berlin, Germany
Studies of the annealing of GaInNAs quantum wells under argon or hydrogen atmosphere
revealed a significant dependency of the annealing behavior on the growth temperature.
Structural investigation by means of transmission electron microscopy reveals the formation
of vacancy type dislocation loops after argon annealing only for quantum wells grown at low
temperature. This was not observed for hydrogen annealing. The formation of these loops
leads to enhanced nonradiative recombination reducing the luminescence efficiency. In
contrast, samples grown at high temperatures show improved luminescence efficiency upon
both annealing atmospheres. This is attributed to the growth-induced formation of different
kinds of defects.
126
8.
JOURNAL OF APPLIED PHYSICS 101, 033113 (2007)
Fabry-Perot effects in InGaN/GaN heterostructures on Si-substrate
C. Hums, T. Finger, T. Hempel, J. Christen, and A. Dadgar
Fakultät für Naturwissenschaften, Institut für Experimentelle Physik, Otto-von-GuerickeUniversität
Magdeburg, Universitätsplatz 2, 39016 Magdeburg, Germany
A. Hoffmann
Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36,
A. Krost
Fakultät für Naturwissenschaften, Institut für Experimentelle Physik, Otto-von-GuerickeUniversität
Magdeburg, Universitätsplatz 2, 39016 Magdeburg, Germany
A strong intensity modulation is found in spatially and angular resolved photoluminescence
spectra of InGaN/GaN heterostructures and quantum wells epitaxially grown on Si (111)
substrates. This Fabry-Perot effect results from the high refractive index contrasts at the
GaN/Si and the Air/InGaN interfaces. It can be used for a wavelength stabilization of the
sample upon temperature change and, e.g., in the case of light emitting diodes, to additionally
reduce the blueshift at increasing injection currents. A simple geometric approach has been
chosen to calculate the influence of layer thickness, absorption and refractive indices, as well
as detection angle. The cavity can be described quantitatively by a simple three layer FabryPerot model. An analytical expression is derived for the external luminescence line shape.
Microphotoluminescence measurements at samples with the silicon substrate locally removed
corroborate the model.
127
14.
PHYSICAL REVIEW B 76, 195203 (2007)
Zn interstitial related donors in ammonia-treated ZnO powders
J. Sann, J. Stehr, A. Hofstaetter, and D. M. Hofmann*
I. Physikalisches Institut, Justus-Liebig-Universität-Giessen, Heinrich-Buff-Ring 16, 35392
Giessen, Germany
A. Neumann and M. Lerch
Institut für Chemie, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin,
Germany
U. Haboeck, A. Hoffmann, and C. Thomsen
Institut für Festkörperphysik, Technische Universität Berlin, Hardenberg Strasse 36, 10623
Berlin, Germany
Received 5 June 2007; revised manuscript received 23 August 2007; published 8 November
2007
ZnO powder heat treated in NH3 atmosphere was investigated by electron paramagnetic
resonance, photoluminescence, and Raman spectroscopy. We find that the treatment creates
Zn interstitials (Zni) and complexesof Zn interstitials and nitrogen atoms substituting oxygen
(Zni-NO). A correlation between the Zni and an exciton at 3.366 eV (I3) can be stated by a
comparison with the PL results; furthermore, the (Zni-NO) complex seems to be related to a
recombination at 3.193 eV.
128
16.
Microscopic theory of quantum dot interactions with quantum light:
local field effect
G.Ya. Slepyan, A. Magyarov, and S.A. Maksimenko
Institute for Nuclear Problems, Belarus State University, Bobruiskaya 11, 220050 Minsk,
Belarus
A. Hoffmann
Institut für Festkörperphysik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
A theory of both linear and nonlinear electromagnetic response of a single QD exposed to
quantum light, accounting the depolarization induced local-field has been developed. Based
on the microscopic Hamiltonian accounting for the electron-hole exchange interaction, an
effective two-body Hamiltonian has been derived and expressed in terms of the incident
electric fieeld, with a separate term describing the QD depolarization. The quantum equations
of motion have been formulated and solved with the Hamiltonian for various types of the QD
excitation, such as Fock qubit, coherent fields, vacuum state of electromagnetic field and light
with arbitrary photonic state distribution. For a QD exposed to coherent light, we predict the
appearance of two oscillatory regimes in the Rabi effect separated by the bifurcation. In the
first regime, the standard collapse-revivals phenomenon do not reveal itself and the QD
population inversion is found to be negative, while in the second one, the collapse{revivals
picture is found to be strongly distorted as compared with that predicted by the standard
Jaynes-Cummings model. For the case of QD interaction with arbitrary quantum light state in
the linear regime, it has been shown that the local field induce a fine structure of the
absorption spectrum. Instead of a single line with frequency corresponding to which the
exciton transition frequency, a duplet is appeared with one component shifted by the amount
of the local field coupling parameter. It has been demonstrated that the strong light-matter
coupling regime arises in the weak-field limit. A physical interpretation of the predicted
effects has been proposed.
129
17.
Journal of Applied Physics 103 07D 140 (2008),
Surface modification of Co-doped ZnO nanocrystals and its effects
on the magnetic properties
A. S. Pereira
Departamento de Química and CICECO, Universidade de Aveiro, P-3810-193 Aveiro,
Portugal
A. O. Ankiewicz
de Física,
W. Gehlhoff and A. Hoffmann
S. Pereira and T. Trindade
CICECO, Universidade de Aveiro, P-3810-193 Aveiro, Portugal
M. Grundmann
Institut für Experimentelle Physik II, Universität Leipzig, D-04103 Leipzig, Germany
M. C. Carmo and N. A. Sobolev
I3 N-Institute for Nanostructures, Nanomodelling and Nanomanufacturing, Aveiro , Portugal
A series of chemically prepared Co2+-doped ZnO colloids has been surface modified either
by growing shells of ZnSe or by the in situ encapsulation in poly (styrene). The surface
modification effects using these two distinct chemical strategies on the magnetic properties of
the nanocrystals were probed by electron paramagnetic resonance (EPR). Structural
characterization by means of x-ray diffraction and transmission electron microscopy gave no
evidence of second phase formation within the detection limits of the used equipment. The
EPR analysis was carried out by simulations of the powderlike EPR spectra. The results
confirm that in the core of these nanocrystals Co was incorporated as Co2+, occupying the
Zn2+ sites in the wurtzite structure of ZnO. Additionally we identify two Co signals
stemming from the nanocrystals’ shell. The performed surface modifications clearly change
the relative intensity of the EPR spectrum components, revealing the core and shell signals.
130
20.
Energy transfer in close-packed PbS nanocrystal films
V. Rinnerbauer, H.-J. Egelhaaf, and K. Hingerl
Christian Doppler Laboratory of Surface Optics, Institute of Semiconductor and Solid State
Physics, University Linz,Altenbergerstrasse 69, A-4040 Linz, Austria
P. Zimmer, S. Werner, T. Warming, and A. Hoffmann
Institute of Solid State Physics, Technical University Berlin, Hardenbergstrasse 36, D-10623
Berlin, Germany
M. Kovalenko, W. Heiss, G. Hesser, and F. Schaffler
Institute of Semiconductor and Solid State Physics, University Linz, Altenbergerstrasse 69, A4040 Linz, Austria
We study the emission properties of close-packed films of PbS nanocrystals that show
emission in theinfrared. In time resolved photoluminescence measurements, we observe a fast
decay time of 400 ps and a slow component between 20 and 80 ns, depending on the
temperature, which are attributed to decay from core and surface states, respectively.
Photoluminescence excitation and temperature-dependent photoluminescence measurements
show that these states are coupled by thermal activation and energy transfer. These transfer
processes efficiently replenish the core states with charge carriers from the surface states,
increasing the photoluminescence yield.
22.
Applied Physics Letters 92, 063116 (2008)
Decay dynamics of neutral and charged excitonic complexes
M. Feucker, R. Seguin, S. Rodt, A. Hoffmann, D. Bimberg
Berlin, Germany
Systematic time-resolved measurements on neutral and charged excitonic complexes (X, XX,
X+, and XX+) of 26 different single InAs/GaAs quantum dots are reported. The ratios of the
decay times are discussed in terms of the number of transition channels determined by the
excitonic fine structure and a specific transition time for each channel. The measured ratio for
the neutral complexes is 1.7 deviating from the theoretically predicted value of 2. A ratio of
1.5 for the positively charged exciton and biexciton decay time is predicted and exactly
matched by the measured ratio indicating identical specific transition times for the transition
channels involved.
131
25.
Material. Research Society Symposium 1040, Q06-09 (2008)
Mn- and Fe-doped GaN for spintronic applications
Enno Malguth1,2, Axel Hoffmann1, Stefan Werner1, Matthew H. Kane3, Ian T. Ferguson3
1Institut für Festkörperphysik, Technische Universität Berlin, Berlin, 10623, Germany
2Microstructural Analysis Unit, University of Technology Sydney, Sydney, 2007, Australia
3School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA,
30332-0245
In the context of ferromagnetic spin-coupling in dilute magnetic semiconductors, we present
optical investigations on Mg co-doped GaMnN and Fe doped GaN. A complex luminescence
feature occurring in Mg co-doped GaMnN around 1 eV was previously attributed to the
internal 4T2(F) -4T1(F) transition of Mn4+ involved in different complexes. Selective
excitation studies indicate the presence of at least three different complexes.
Photoluminescence excitation spectra suggest that the internal Mn3+ transition may represent
an excitation mechanism. Magneto photoluminescence spectra indicate equal g values for the
ground and excited state. Low temperature infrared absorption spectra of Fe doped GaN allow
to unambiguously establish the electronic structure of the Fe2+ center in GaN. Our results
suggest that the Fe2+ (5T2) state is stabilized against Jahn-Teller coupling by the reduced
site-symmetry of the hexagonal lattice.
29.
Journal of Physics Condenced MAtter 20 (2008), 454211
GaN/AlN quantum dots for single qubit emitters
M. Winkelnkemper, R. Seguin, S. Rodt, A. Hoffmann, D. Bimberg
Berlin, Germany
We study theoretically the electronic properties of c-plane GaN/AlN quantum dots (QDs)
with the focus on their potential as sources of single polarized photons for future quantum
communication systems. Within the framework of eight-band k · p theory we calculate the
optical interband transitions of the QDs and their polarization properties. We show that an
anisotropy of the QD confinement potential in the basal plane (e.g. QD elongation or strain
anisotropy) leads to a pronounced linear polarization of the ground-state and excited-state
transitions. An externally applied uniaxial stress can be used to either induce a linear
polarization of the ground-state transition for emission of single polarized photons or even to
compensate the polarization induced by the structural elongation.
132
30.
Physical Review B 79 (2009), 035307
Influence of substrate surface polarity on homoepitaxial growth of ZnO
layers by chemical vapour deposition
Markus R. Wagner, Til P. Bartel, Ronny Kirste, and Axel Hoffmann
Institute of Solid State Physics, TU Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany
Joachim Sann, Stefan Lautenschläger, and Bruno K. Meyer
I. Physics Institute, Justus Liebig University, Heinrich-Buff-Ring 16, 35592 Giessen,
Germany
C. Kisielowski
National Center for Electron Microscopy, Material Science Division,Lawrence Berkeley
National Laboratory, One cyclotron road, Berkeley, 94720, USA
The influence of the substrate polarity (Zn-polar or O-polar) on the structural and optical
properties of homoepitaxial ZnO epilayers grown by chemical vapor deposition is
investigated. High resolution TEM images clearly demonstrate the control of the epilayer’s
polarity by the substrate. A small compressive strain of cc = 3 · 10−4 is observed in both
epilayers and XRD measurements indicate a superior structural quality of the epilayers
compared to the substrate. Cross-sectional Raman scattering also demonstrates the growth of
high quality epilayers, although high strain is present within the substrate. The phonon
deformation potential parameters of the strain sensitive E2(high) Raman mode are determined
to a = −730 cm−1 and b = −1000 cm−1. Differences in the excitonic luminescence including
the appearance of new emission lines and an increased full width at half maximum in O-face
epilayers are observed. It is suggested that the impurity diffusion from the substrate to the
layer is affected by the substrate surface polarity with lower impurity concentrations in the
Zn-polar film, compared to the O-polar epilayer.
133
34.
Physical Review Letters 102 (2009), 023601
Field-matter strong coupling in two-level quantum systems with broken
inversion symmetry
O.V. Kibis1, G.Ya. Slepyan2, S.A. Maksimenko2, and A. Hoffmann3
1Department of Applied and Theoretical Physics, Novosibirsk State Technical University,
Karl Marx Avenue 20, 630092 Novosibirsk, Russia
2Institute for Nuclear Problems, Belarus State University, Bobruyskaya St. 11, 220050 Minsk,
Belarus
3 Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, D10623 Berlin, Germany
We demonstrate theoretically the parametric oscillator behavior of a two-level quantum
system with broken inversion symmetry exposed to a strong electromagnetic field. A
multitude of resonance frequencies and additional harmonics in the scattered light spectrum as
well as altered Rabi frequency are predicted to be inherent to such systems. In particular,
dipole radiation at the Rabi frequency appears to be possible. Since the Rabi frequency is
controlled by the strength of coupling electromagnetic field, the effect can serve for the
frequency-tuned parametric amplification and generation of electromagnetic waves.
Manifestation of the effect is discussed for III-nitride quantum dots with strong build-in
electric field breaking the inversion symmetry. Terahertz emission from arrays of such
quantum dots is shown to be experimentally observable.
39.
physica status solidi (RRL), A 3 (2009), 16
Nitrogen incorporation in homoepitaxial ZnO CVD epilayers
S. Lautenschlaeger, S. Eisermann, B.K. Meyer
I. Physics Institute, Justus Liebig University, Heinrich-Buff-Ring 16, 35592 Giessen,
Germany
G. Callsen, M.R. Wagner, A. Hoffmann
Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, D-10623
Berlin, Germany
ZnO:N thin films have been deposited on oxygen and zinc terminated polar surfaces of ZnO.
The nitrogen incorporation in the epilayers using NH3 as doping source was investigated as a
function of the growth temperature in the range between 380°C and 580°C. We used Raman
spectroscopy and low temperature photoluminescence to investigate the doping properties. It
turned out that the nitrogen incorporation strongly depends on both the surface polarity of the
epitaxial films and the applied growth temperatures. In our CVD process low growth
temperatures and Zn-terminated substrate surfaces clearly favour the nitrogen incorporation of
ZnO.
134
41.
J. Vac. Sci. Technol. A 26 (2008), 1023
Optical characterization of InN layers grown by high-pressure chemical
vapour deposition
M. Alevli,a_ R. Atalay, G. Durkaya, A. Weesekara, A. G. U. Perera, and N. Dietz
Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303
R. Kirste and A. Hoffmann
Berlin, Germany
The optical properties of InN layers grown by high-pressure chemical vapor deposition have
been studied. Raman, infrared reflection, and transmission spectroscopy studies have been
carried out to investigate the structural and optical properties of InN films grown on sapphire
and GaN/sapphire templates. Results obtained from Raman and IR reflectance measurements
are used to estimate the free carrier concentrations, which were found to be varying from mid
1018 to low 1020 cm−3. The values for free carrier concentrations are compared to optical
absorption edge estimates obtained from optical transmission spectra analysis. The analysis
shows that optical absorption edge for InN shifts below 1.1 eV as the free carrier
concentration decreases to low 1018 cm−3.
135
9.3
Department III
Prof. Dr. rer. nat. Mario Dähne
Prof. em. Dr.-Ing. Hans-Eckhart Gumlich
9.3.0 Staff
Secretary
Angela Berner (part time)
Technical staff
Gerhard Pruskil
Senior Scientists
Dr. Holger Eisele
Dr. Andrea Lenz
Dr. Rainer Timm
Dr. Martina Wanke (until 30.11.2008)
PhD candidates (status of 31.12.2008 - thesis completed = c)
Dipl.-Phys. Jan Grabowski
Dipl.-Phys. Kai Hodeck
Dipl.-Phys. Lena Ivanova
Dipl.-Phys. Andrea Lenz (c)
Dipl.-Phys. Rainer Timm (c)
Dipl.-Phys. Martina Wanke (c)
Diploma students (status of 31.12.2008 – thesis completed = c)
Martin Franz
Florian Genz
Sylvia Hagedorn (c)
Britta Höpfner
Karolin Löser (c)
Nadine Oswald
Grit Petschick (c)
Christopher Prohl
Matthias Vetterlein
136
137
9.3.1 Summary of activities
The main research subject of the group of Prof. M. Dähne is the investigation of the structural
and electronical properties of semiconductor surfaces, interfaces and nanostructures. This
includes in-situ sample preparation by molecular beam epitaxy (MBE) or reactive epitaxy. In
the experiments, special emphasis lies on the use of local probes, such as scanning-tunneling
microscopy (STM) and spectroscopy (STS), also in cross-sectional mode (XSTM and XSTS).
Complementary information is obtained from angle-resolvel photoelectron spectroscopy
(ARPES) with synchrotron radiation at the Berlin storage ring BESSY. All experiments are
performed in ultra-high vacuum (UHV).
There are mainly three experimental setups:
1. An STM/STS chamber with an attached multi-purpose preparation chamber containing
LEED, sputter gun, sample heating, and effusion cells
2. A chamber designed especially for XSTM/XSTS experiments, including in-situ sample
cleavage and lateral tip positioning
3. An MBE chamber with RHEED and an attached STM for in-situ preparation and
structural studies of III-V surfaces and nanostructures
For ARPES experiments, chambers from Prof. Kaindl at the Freie Universität Berlin, from
Prof. Laubschat at the Technische Universität Dresden, and from Prof. Riley, LaTrobe
University are used.
Recent results are listed in the following:
1. Atomic structure of capped nanostructures. Using XSTM and XSTS, the atomic
structure, local chemical composition and local electronic properties of semiconductor
nanostructures were investigated. For this purpose, a cross-sectional (110) surface is prepared
in-situ by sample cleavage and then studied by the STM tip. The samples were provided by
department I, Qimonda, Osram, the Ioffe Institute in St. Petersburg, the Fritz-Haber-Institut in
Berlin, the University of Sheffield, the University of Cambridge, and the University of New
Mexico. The following results were obtained:
(a) The first atomically resolved XSTM data of non-polar GaN (1 1 00) surfaces could be
taken and the nature of the surface states could be determined [10]. Also the nature of
dislocations in GaN was studied.
(b) The influence of small amounts of nitrogen on the InAs quantum dot growth was studied,
resulting in remarkably strong dissolution effects and subsurface intermixing [7].
(c) Novel concepts of large InAs quantum dot growth using a dots-in-a-well structure were
tested, which, however, can easily lead to defective dots containing nanovoids [5]
(d) The first XSTM data on submonolayer quantum dots were taken [1-3].
(e) The astonishing self-organized formation of GaSb quantum rings instead of compact
quantum dots was observed [9,11]. In this type-II system, also a novel contrast mechanism
was found based on tip-induced band bending, and the type-II behavior could be observed
directly in the spectroscopy data.
(f) The structure of InAs quantum dots was found to be strongly modified upon capping
[8,12].
2. Rare earth silicide nanostructures. With STM and ARPES, the atomic structure and
electronic dispersion of epitaxial rare earth silicide layers and self-organized nanowires were
studied. For the first time, a toroidal analyzer was used allowing to directly image the
constant energy surfaces in k||-space. It was found that nanowires form on (111) terraces of
the Si(557) surface, which show both structural properties and the two-dimensional electronic
dispersion from disilicides found on Si(111) [6]. Interestingly, nanowires from the same
disilicides on Si(001) are characterized by a one-dimensional electronic structure, which is
138
related to the different c-axis orientation of the silicide and its strongly anisotropic electronic
properties. Furthermore, interesting sub-monolayer nanowire structures could be found.
3. InAs wetting layer and quantum dot growth. With MBE and in-situ STM, the different
stages of InAs quantum dot growth were studied, starting with submonolayer InAs coverages
up to the development of quantum dots. Here, structures on both the c(4x4) and the β2(2x4)
growth surfaces were studied. Preliminary results show that dislocations in the surface
reconstruction of the substrate are formed, where the wetting layer starts to grow. The
quantum dots show similar structural features as observed previously. More detailed studies
are under way.
139
9.3.2 Publications
1.
Novel concepts for ultrahigh-speed quantum-dot VCSELs and edge-emitters
N.N. Ledentsov, F. Hopfer, A. Mutig, V.A. Shchukin, A.V. Sava’lev, G. Fiol, M.
Kuntz, V.A. Haisler, T. Warming, E. Stock, S.S. Mikhrin, A.R. Kovsh, C. Bornholdt, A.
Lenz, H. Eisele, M. Dähne, N.D. Zakharov, P. Werner, and D. Bimberg
Physics and Simulation of Optoelectronic Devices XV, edited by M. Osinski, F.
Henneberger, and Y. Arakawa, Proc. SPIE 6468, 646810 (2007)
2.
20 Gb/s 85°C error-free operation of VCSELs based on submonolayer deposition
of quantum dots
F. Hopfer, A. Mutig, G. Fiol, M. Kuntz, V.A. Shchukin, V.A. Haisler, T. Warming, E.
Stock, S.S. Mikhrin, I.L. Krestnikov, D.A. Livshits, A.R. Kovsh, C. Bornholdt, A. Lenz,
H. Eisele, M. Dähne, N.N. Ledentsov, and D. Bimberg
IEEE Journal of Selected Topics in Quantum Electronics 13, 1302 (2007)
3.
Submonolayer quantum dots for high speed surface emitting lasers
N.N. Ledentsov, D. Bimberg, F. Hopfer, A. Mutig, V.A. Shchukin, A.V. Sava’lev, G.
Fiol, E. Stock, H. Eisele, M. Dähne, D. Gerthsen, U. Fischer, D. Litvinov, A.
Rosenauer, S.S. Mikhrin, A.R. Kovsh, N.D. Zakharov, and P. Werner
Nanoscale Research Letters 2, 417 (2007)
4.
Erratum: “Atomically resolved structure of InAs quantum dots” [Appl. Phys. Lett.
78, 2309 (2001)]
H. Eisele and K. Jacobi
5*.
Structure of InAs quantum dots-in-a-well nanostructures
A. Lenz, H. Eisele, R. Timm, L. Ivanova, H.-Y. Liu, M. Hopkinson, U.W. Pohl, and M.
Dähne
Physica E 40, 1988 (2008)
6*.
Formation of dysprosium silicide nanowires on Si(557) with two-dimensional
electronic structure
M. Wanke, K. Löser, G. Pruskil, and M. Dähne
7*.
Nitrogen-induced intermixing of InAsN quantum dots with the GaAs matrix
L. Ivanova, H. Eisele, A. Lenz, R. Timm, M. Dähne, O. Schumann, L. Geelhaar, and H.
Riechert
8*.
The atomic structure of quantum dots
Mario Dähne, Holger Eisele, and Karl Jacobi
Semiconductor Nanostructures, ed. by D. Bimberg (Springer, Berlin, Heidelberg, 2008),
p. 123
9*.
Quantum ring formation and antimony segregation in GaSb/GaAs nanostructures
R. Timm, A. Lenz, H. Eisele, L. Ivanova, M. Dähne, G. Balakrishnan, D.L. Huffaker, I.
Farrer, and D.A. Ritchie
Journal of Vacuum Science and Technology B 26, 1492 (2008)
140
10*. Surface states and origin of the Fermi level pinning on non-polar GaN (1 1 00)
surfaces
L. Ivanova, S. Borisova, H. Eisele, M. Dähne, A. Laubsch, and Ph. Ebert
11*. Self-organized formation of GaSb/GaAs quantum rings
R. Timm, H. Eisele, A. Lenz, L. Ivanova, G. Balakrishnan, D.L. Huffaker, and M.
Dähne
12*. Change of InAs/GaAs quantum dot shape and composition during capping
H. Eisele, A. Lenz, R. Heitz, R. Timm, M. Dähne, Y. Temko, T. Suzuki, and K. Jacobi
13.
Das Phänomen der Zeit in der Physik
Hans-Eckhardt Gumlich in
“Was ist Zeit?“, A. Groh (Hrsg.), Weidler-Verlag Berlin
141
9.3.3 Invited talks
Eisele, Holger
Electronic and structural properties of the GaN (1 1 00) surface
Univ. Magdeburg, Germany, November 2008
Gumlich, Hans-Eckhart Wissenschaft und Widerspruch. Rationalität als Bildungsziel?
Podiumsdiskussion beim Triangelkolloquium der Guardini-Stiftung,
Wittenberg, Germany, November 2007
Gumlich, Hans-Eckhart Die Zeiten der Physiker
Kongress Wissen, Kreativität und Transformation von
Gesellschaften, Wien, Austria, December 2007
Gumlich, Hans-Eckhart Die Physik der Farben
Ringvorlesung der Arbeitsstelle für „Semiotik and Structural
Analysis“, Technischen Universität Berlin, Germany, November
2008
Timm, Rainer
Formation, atomic structure, and electronic properties of GaSb
quantum dots in GaAs
IBM Almaden Research Center, San Jose, USA, January 2008
Timm, Rainer
Growth, atomic structure, and electronic properties of
GaSb/GaAs nanostructures studied by cross-sectional STM
Lund University, Sweden, January 2008
Wanke, Martina
Formation of rare earth silicide nanowires on silicon surfaces
with one- and two-dimensional band structure
Univ. Hannover, Germany, September 2008
142
143
9.3.4 PhD theses
Lenz, Andrea
Atomic structure of capped In(Ga)As and GaAs quantum dots
for optoelectronic devices
January 2008
Timm, Rainer
Formation, atomic structure, and electronic properties of GaSb
quantum dots in GaAs
December 2007
Wanke, Martina
Rare earth silicide nanowires on silicon surfaces
November 2008
Hagedorn, Sylvia
Aufbau und Inbetriebnahme einer MBE-STM-Apparatur für die
Untersuchung von Quantenpunkten
March 2007
Löser, Karolin
Strukturelle und elektronische Eigenschaften von SilizidNanodrähten auf Si(557)
June 2007
Petschick, Grit
Realisierung eines Rastertunnelmikroskops für die Ausbildung
January 2007
144
145
9.3.6 Abstracts of selected papers of department III
5.
Physica E 40, 1988 (2008)
Structure of InAs quantum dots-in-a-well nanostructures
A. Lenza, H. Eiselea,b, R. Timma, L. Ivanovaa, H.-Y. Liuc, M. Hopkinsonc, U.W. Pohla,
and M. Dähne
a
Institut für Festkörperphysik, EW 4-1, Technische Universität Berlin, 10623 Berlin, Germany
b
Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
c
Department of Electronic and Electrical Engineering, University of Sheffield,
Sheffield S1 3JD, UK
InAs/InGaAs quantum dots-in-a-well nanostructures based on GaAs are a promising
candidate for optoelectronic devices with the important emission wavelength of 1.3 µm. We
present cross-sectional scanning tunneling microscopy data, showing material reorganization
depending on the process of GaAs cap layer growth on top of the quantum dot (QD)
nanostructures. QDs capped with 2 nm GaAs prior to an extended growth interruption have a
truncated pyramidal shape, typical base lengths of 20–25 nm, and 5–7 nm height. Those
capped by a thicker GaAs layer show identical shapes, but their sizes are generally larger with
about 30 nm base length and 6–9 nm height. Furthermore, some of these large QDs contain
nanovoids, which form during the capping process and can be avoided in the case of a thin
GaAs cap layer.
6.
Formation of dysprosium silicide nanowires on Si(557) with twodimensional electronic structure
M. Wanke, K. Löser, G. Pruskil, and M. Dähne
Berlin, Germany
The self-organized growth of dysprosium silicide nanowires on Si(557) has been studied
using scanning tunneling microcopy and angle-resolved photoelectron spectroscopy. The
nanowires grow on the (111) facets of the Si(557) surface with lengths exceeding 1000 nm
and widths of 3–5 nm. Their metallic electronic structure shows a two-dimensional behavior
with a strong dispersion, which is both parallel and perpendicular to the nanowires. For Dy
coverages of around 2 Å, it is demonstrated that the nanowires consist of hexagonal DySi2
monolayers, while at higher coverages they are predominantly formed from Dy3Si5
multilayers.
146
7.
Nitrogen-induced intermixing of InAsN quantum dots with the GaAs
matrix
L. Ivanova,1 H. Eisele,1 A. Lenz,1 R. Timm,1 M. Dähne,1 O. Schumann,2 L. Geelhaar,2
and H. Riechert2
1
Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10623
Berlin, Germany
2
Qimonda (formerly Infineon Technologies), 81730 München, Germany
We investigated the influence of nitrogen incorporation on the growth of InAsN/GaAs
quantum dots (QDs) using cross-sectional scanning tunneling microscopy. Nitrogen exposure
during InAs growth leads to a rather strong dissolution and the formation of extended almost
spherical InGaAs QDs with a very low nitrogen content. Nitrogen atoms are instead observed
in the surrounding GaAs matrix, and indium atoms are even found underneath the nominal
base plane of the QDs. These effects are related to a rather low solubility of nitrogen within
InAs, leading to high strain between indium-rich QDs and the surrounding nitrogen-rich
matrix.
8.
Semiconductor Nanostructures, ed. by D. Bimberg (Springer, Berlin, Heidelberg, 2008),
p. 123
The atomic structure of quantum dots
Mario Dähne1, Holger Eisele2, and Karl Jacobi3
Berlin, Germany daehne@physik.tu-berlin.de
2
Berlin, Germany ak@physik.tu-berlin.de
3
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
jacobi@fhi-berlin.mpg.de
1
In this chapter, the atomic structure of both uncapped and buried quantum dots is described as
derived from scanning tunneling microscopy in both top-view and cross-sectional geometry.
Important conclusions are drawn also on the growth processes during quantum dot formation
as well as during overgrowth. It is demonstrated that uncapped InAs quantum dots on
GaAs(001) have a pyramidal shape with dominating {137} side facets and – in the case of
larger dots – also {101} and {111} side facets. Buried InAs and InGaAs quantum dots, in
contrast, are characterized by a truncated pyramidal shape with a (001) top facet and rather
steep side facets. In addition, segregation processes during capping lead to strong intermixing
and – under special overgrowth conditions – even to concave top facets or to the formation of
nanovoids. Buried GaSb quantum dots are found to be much smaller, but also show a
truncated pyramidal shape and strong intermixing effects. The experimental results will be
discussed in the framework of the strain-induced segregation processes occurring during the
different stages of quantum dot formation and overgrowth.
147
9.
Journal of Vacuum Science and Technology B 26, 1492 (2008)
Quantum ring formation and antimony segregation in GaSb/GaAs
nanostructures
R. Timm, A. Lenz, H. Eisele, L. Ivanova, and M. Dähne
G. Balakrishnan and D. L. Huffaker
Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico
87106
I. Farrer and D. A. Ritchie
Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
GaSb quantum rings in GaAs were studied by cross-sectional scanning tunneling microscopy.
The quantum rings have an outer shape of a truncated pyramid with typical lateral extensions
between 10 and 30 nm and heights between 1 and 3 nm, depending on the molecular beam
epitaxy growth conditions. A clear central opening of varying diameter and more or less
conical shape, filled with GaAs, is characteristic for the GaSb rings. The self-organized
formation of quantum rings during the growth and subsequent fast overgrowth of GaSb
quantum dots is attributed to a combination of large strain with strong Sb segregation. The
latter is enabled by extensive group-V atomic exchange reactions at the GaSb/GaAs
interfaces, which are quantitatively evaluated from the atomically resolved microscopy data.
10.
Surface states and origin of the Fermi level pinning on non-polar
GaN (1 1 00) surfaces
L. Ivanova,1 S. Borisova,2 H. Eisele,1 M. Dähne,1 A. Laubsch,3 and Ph. Ebert2
1
Berlin, Germany
2
Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
3
OSRAM Opto-Semiconductors GmbH, Leibnizstrasse 4, 93055 Regensburg, Germany
GaN (1 1 00) cleavage surfaces were investigated by cross-sectional scanning tunneling
microscopy and spectroscopy. It is found that both the N and Ga derived intrinsic dangling
bond surface states are outside of the fundamental band gap. Their band edges are both
located at the Γ point of the surface Brillouin zone. The observed Fermi level pinning at 1.0
eV below the conduction band edge is attributed to the high step and defect density at the
surface but not to intrinsic surface states.
148
11.
Self-organized formation of GaSb/GaAs quantum rings
R. Timm,1 H. Eisele,1,2 A. Lenz,1 L. Ivanova,1 G. Balakrishnan,3 D. L. Huffaker,3 and M.
Dähne1
1
2
Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
3
Center for High Technology Materials, University of New Mexico, Albuquerque, New
Mexico 87106, USA
Ring-shaped GaSb/GaAs quantum dots, grown by molecular beam epitaxy, were studied
using cross-sectional scanning tunneling microscopy. These quantum rings have an outer
shape of a truncated pyramid with baselengths around 15 nm and heights of about 2 nm but
are characterized by a clear central opening extending over about 40% of the outer baselength.
They form spontaneously during the growth and subsequent continuous capping of
GaSb/GaAs quantum dots due to the large strain and substantial As-for-Sb exchange reactions
leading to strong Sb segregation.
12.
Change of InAs/GaAs quantum dot shape and composition during capping
H. Eisele,1,2 A. Lenz,1 R. Heitz,1 R. Timm,1 M. Dähne,1 Y. Temko,3, T. Suzuki,3 and K.
Jacobi3
1
Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623
Berlin, Germany
2
Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
3
Abteilung für Physikalische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft,
Faradayweg 4-6,14195 Berlin, Germany
Using plan-view and cross-sectional scanning tunneling microscopy, the shape and
composition of InAs/GaAs quantum dots are investigated before and after capping by GaAs.
During capping, the original pyramidally shaped quantum dots become truncated, resulting in
a flat (001) top facet and steeper side facets. The InAs quantum dots are found to be
intermixed at their top with GaAs due to material rearrangement. Since the bottom interface
of quantum dots and wetting layer is always sharp, this intermixing occurs during capping and
not during quantum dot growth. Considering strain energies, a model for the capping is
presented.
149
9.4
Department IV
Prof. Dr. rer. nat. Michael Kneissl
Prof. Dr. rer. nat. Wolfgang Richter (retired)
Prof. Dr. rer. nat. Norbert Esser (S-professorship with ISAS)
9.4.0 Staff
Secretary
Claudia Hinrichs (part time)
Angela Berner (part time)
Technical staff
Matthias Dreier (since 23.1.2008)
Engelbert Eder
Christof Maerker (until 31.1.2008)
Senior scientists
Dr. Patrick Vogt
Dr. Markus Pristovsek
Dr. Sandhya Chandola
Dr. Simona Silaghi (until 28.2.07)
PhD Yang Minghong (until 31.7.07)
PhD candidates (status of 31.12.2008 – thesis completed = c)
Dipl.-Phys. Thomas Bruhn
Dipl.-Phys. Ralph Debusmann
Dipl.-Phys. Marcel Ewald
Dipl.-Phys. Christian Friedrich
Dipl.-Phys. Tim Kolbe
Dipl.-Phys. Raimund Kremzow
Dipl.-Phys. Martin Leyer
Ms. Sci. Neysha Lobo
Dipl.-Phys. Jan-Robert van Look
Dipl.-Phys. Christian Meißner
Dipl.-Phys. Regina Paßmann (until 31.12.08) (c)
Dipl.-Phys. Simon Ploch
Dipl.-Phys. Jessica Schlegel
Dipl.-Phys. Joachim Stellmach
Dipl.-Phys. Jens Raß
150
Diploma students (status of 31.12.2008 – thesis completed = c)
Tobias Arlt (c)
Thomas Bruhn (c)
Marcel Ewald (c)
Martin Frentrup
Christian Friedrich (c)
Matthias Guderian (c)
Marc Hoffmann
Michael Högele
Tim Kolbe (c)
André Kruse
Viola Küller (c)
Simon Ploch (c)
Vanessa Rackwitz (c)
Linda Riele
Marc-Antonius Rothe
Özgür Savas
Lars-Peter Scheller (c)
Jessica Schlegel (c)
Matthias Schmies
Toni Sembdner
Joachim Stellmach (c)
Marek Warzecha (c)
151
9.4.1
The “Experimental Nanophysics and Photonics” research group is exploring a wide range
of topics including metalorganic vapor phase epitaxy (MOVPE) of group III-nitride
compounds and nanostructures, the study of optical and electronic properties of
semiconductor surfaces and interfaces, and the development of novel optoelectronic devices.
The material system AlN-GaN-InN covers an extraordinarily wide wavelength range, that
includes the entire visible spectrum and ranges from the deep ultraviolet (UV) to the near
infrared. This exceptional versatility makes InAlGaN heterostructures exceedingly interesting
for numerous new device applications. These include near and deep ultraviolet (UV)
InAlGaN light emitting diodes (LEDs), high power and high brilliance blue and green laser
diodes, GaN-based semiconductor disk lasers (SCDL), vertical cavity surface emitting lasers
(VCSELs) and single photon emitter (SPE). These new devices are a key enabler for a
number of applications, including e.g. the purification of drinking water, biomedical
diagnostics, laser projection displays, and secure data communication. The research activities
in the “Experimental Nanophysics and Photonics” group are conducted in close collaboration
with the GaN Optoelectronics BUSINESS AREA at the Ferdinand-Braun-Institut für
Höchstfrequenztechnik (FBH) located on the Science and Technology Campus in BerlinAdlershof. By combining competencies in both basic and applied research, our mission is to
establish a European center of excellence in the field of GaN materials growth and devices.
In the last two years we were able to secure third-party funding for a number of research
activities. At the beginning of 2008 the project “Materials for high brilliance green laser
diodes” was launched as part of the newly established Collaborative Research Center (SFB
787) “Semiconductor Nanophotonics”. In May of 2008 we started the development of
InGaN quantum well laser heterostructures on semipolar growth surfaces in connection with
the new DFG research group “Polarisation field control in nitride light emitters” (FOR
957). Funded by the German Federal Ministry of Education and Research (BMBF) the joint
research project „Deep UV LEDs“ was established in July 2008 targeting the development of
highly efficient light emitting diodes in the UVB and UVC spectral range. September 2008
marked the launch of the “RAINBOW” Initial Training Network (ITN) funded by the
European Union (EU), with the goal to develop high quality InN layers and heterostructures
for applications in solar cells and high frequency electronics. In the past two years we have
also obtained a number of individual grants from the German Research Foundation (DFG).
These include the development of GaN-based semiconductor disk lasers (SCDL) for
emission in the blue-violet wavelength range and the investigation of nanostructure growth
during metalorganic vapour phase epitaxy using in-situ scanning tunnelling microscopy.
This new in-situ technique allows time resolved measurements of the growth surface in a
MOVPE reactor on an atomic scale. Time resolved Oswald ripening of InAs quantum dots
was measured in-situ for the first time. Close collaboration have been also established on the
topic of modelling and simulation of GaN devices with Prof. Weng Chow at Sandia National
Laboratory (USA), Dr. Joachim Piprek at the NUSOD Institute (USA), and Prof. Bernd
Witzigmann (ETH Zürich/University of Kassel).
In joint cooperation with the Ferdinand-Braun-Institute (FBH) we were able to establish a
technology base for InAlGaN materials growth and device fabrication that yielded GaN-based
violet laser diodes with state-of-the-art performance. InGaN MQW lasers diodes grown on
low dislocation density GaN substrate were demonstrated with threshold current densities as
low as 3.5 kA/cm2 for an emission wavelength near 405 nm and a light output power of more
than 500 mW per facet. We were able to demonstrate optically pumped violet and blue
wavelength lasers with emission between 390 nm and 445 nm. Growth studies on non- and
152
semipolar GaN yielded InGaN MQW LEDs on m-plane GaN substrates with mW output
power emitting near 410 nm. Just recently we were also able to realize first UV LEDs
emitting near 350 nm and 320 nm respectively. In 2007 a new Thomas Swan Close-Coupled
Showerhead MOVPE reactor was installed at TU Berlins Nanophotonic Center. The MOVPE
systems features in-situ reflectometer and curvature sensors as well and windows for in-situ
straylight and absorption measurements in the gas phase and is dedicated to the growth of
GaN-based nanostructures and devices. The new reactor will be critical for the investigation
of high pressure growth of p-doped AlGaN layers and high efficiency InGa(Al)N quantum
wells. Our expertise on in-situ growth monitoring was used to determine the growth modes of
InN and InGaN. We reported for the first time InN quantum dots on GaN with a density of
1011cm-2 and a size of less than 20 nm. We were able to show that InN quantum dots grow in
the Vollmer-Weber growth mode, while InGaN layers with less than 50% of indium content
were found to grow in the Stranski-Krastanov mode. From in-situ ellipsometry measurements
and ex-situ X-ray diffraction studies the InGaN critical thickness was determined for a range
of indium mole fractions and a correlation with theoretical models was established. In close
collaboration with the University of Parma the manganese incorporation into InP and InAsP
films by MOVPE was investigated. InAsP alloys constitute a very promising material system
for the realization of magnetic semiconductors. We were able to demonstrate that the depth of
the Mn acceptor level can be tailored over a wide range by varying the arsenic mole fraction
in the InAsP layers.
The technological development in the field of optoelectronic devices like laser diodes or solar
cells as well as for novel sensor concepts focuses strongly on group-III nitrides. Such devices
very often consist of multi layer structures with individual layer thickness in the range of a
few nm. The structural and electronic properties of these surfaces and interfaces play a crucial
role for the design and functionality of the device structures. In the field of surface analysis
we have focused on group-III nitrides such as InN, GaN and InGaN. For these investigations
the surface preparation of clean III-nitride surfaces is still a puzzling problem. For InN and
InGaN we could demonstrate strategies of such preparation methods by annealing and we
were able to demonstrate the first reconstructions observed on an InGaN surface. Another
important direction of our work is the functionalization of III-V surfaces by organic
molecules. Organic molecules are capable to functionalize semiconductor surfaces thus
enabling the combination of the selective and electronic properties of the organic molecules
with the technological applications of semiconductor devices. This combination is considered
to play a key role for future developments in the field of sensors and biotechnology. Our
work, concerning this issue, is focused on the interface formation between small organic
(ring) molecules and III-V surfaces. Changes of structural aspects on an atomic scale and the
related changes of the electronic surface properties upon deposition of organic molecules are
crucial for the technological application. The surface analysis is part of the close cooperation
with Prof. Norbert Esser and Prof. Wolfgang Richter. Prof. Norbert Esser, Director of the
Institute for Analytical Sciences (ISAS) in Berlin and Dortmund, is associated with our group
holding an S-professorship at the TU Berlin. Prof. Wolfgang Richter, now at the physics
department of the University of Rome “Tor Vergata”, continued to serve his scientific
responsibilities at the department IV such as leading his ongoing projects at TU Berlin,
advising PhD students and collaborating in new projects.
153
9.4.2 Publications
1.
Nitride emitters go nonpolar
Ulrich T. Schwarz & M. Kneissl
phys. stat. sol. (rapid research letters) 1, A44 (2007).
2.* Influence of quantum-well-barrier composition on gain and threshold current in
AlGaN lasers
W. W. Chow, M. Kneissl, J. E. Northrup, N. M. Johnson
Appl. Phys. Lett. 90, 101116 (2007)
3.
High-Q-preserving coupling between a spiral and a semicircle μ-cavity
G.D. Chern, G.E Fernandes, R.K. Chang, Q. Song, L. Xu, M. Kneissl, N.M. Johnson
Optics Letters 32, 1093 (2007), 9, 1093
4.* Ultraviolet semiconductor laser diodes on bulk AlN
Michael Kneissl, Zhihong Yang, Mark Teepe, Cliff Knollenberg, Oliver Schmidt, Peter
Kiesel, Noble M. Johnson, Sandra Schujman and Leo J. Schowalter
J Appl. Phys. 101,123103 (2007)
5.
Homoepitaxial growth rate measurements using in-situ Reflectance Anisotropy
Spectroscopy
Kaspari Christian; Pristovsek M.; Richter W.
Journal of Crystal Growth, Elsevier, 298 (2007), 46
6.
Optical anisotropy of cyclopentene terminated GaAs(001) surfaces
Passmann, Regina; Kropp, M.; Bruhn, T.; Fimland, B. O.; Gossard, A. C.; Richter, W.;
Esser, N.; Vogt, P.
Applied Physics A, Springer, 87 (2007), Nr. 3, S.469-473
7.
In-situ Scanning Tunnelling Microscopy during Metal-Organic Vapour Phase
Epitaxy
Pristovsek, Markus; Rähmer, Bert; C, Markus; Kremzow, Raimund; Richter, Wolfgang
Journal of Crystal Growth, Elsevier Science, 298 (2007), S.8-11
8.
Segregation and desorption of antimony in InP in MOVPE
Weeke, Stephan; Leyer, Martin; Pristovsek, Markus; Brunner, Frank; Weyers, Markus;
Richter, Wolfgang
Journal of Crystal Growth, Elsevier Science, 298 (2007), S.159-162
9.
Varying the Overlap of Direct-Coupling between Spiral and Semicircle
Semiconductor Microdisk Lasers
Fernandes, Gustavo E.; Chern, Grace D.; Song, QingHai; Xu, Lei; Kneissl, Michael;
Johnson, Noble M.; Chang, Richard K.
Proc. of the 9th. Int. Conf. on Transparent Optical Networks. 4. New York: IEEE, 2007,
S. 212 - 215
10. Influence of the barrier composition on the light output of InGaN multiplequantum-well ultraviolet light emitting diods
Knauer, A.; Kueller, V.; Einfeldt, S.; Hoffmann, V.; Kolbe, T.; van Look, J.-R.; Piprek,
J.; Weyers, M.; Kneissl, M.
SPIE Photonics East. 6797. Bellingham, USA: SPIE, 2007, S. 67970x-1
154
11. Analysis of Wavelength-Dependent Performance Variations of GaN-Based
Ultraviolet Laser
Piprek, Joachim; Wenzel, Hans; Kneissl, Michael
SPIE Proceedings. 6766. Bellingham, USA: SPIE, 2007, S. 67660H
12. Optimization of InGaN/(In,Al,Ga)N based near UV-LEDs by MQW strain
balancing with in-situ wafer bow sensor
A. Knauer, T. Kolbe, S. Einfeldt, M. Weyers, M. Kneissl, and T. Zettler
phys. stat .sol. (a) (2008)
13. Interplay of screening and band gap renormalization effects in near UV InGaN
light emitting diodes
H. Wenzel, A. Knauer, T. Kolbe and M. Kneissl
IEEE Proceedings 8th International Conference on Numerical Simulation of
Optoelectronic Devices, 5 (2008)
14.* Influence of the growth temperature on the structural and optical properties of
InGaN multi-quantum-wells for 405 nm laser diodes
V. Hoffmann, A. Knauer, F. Brunner, U. Zeimer, S. Einfeldt, M. Weyers, M. Kneissl, G.
Tränkle, J.R. van Look, K. Kazlauskas, S. Jursenas
J. Cryst. Growth 310, 4525 (2008)
15. Properties of InMnP (001) grown by MOVPE
M. Pristovsek, A. Philippou, B. Rähmer, W. Richter
J. Crystal Growth 310, 4046 (2008)
16. Effect of the AlN nucleation layer growth on AlN material quality
O. Reentilä, F. Brunner, A. Knauer, A. Mogilatenko, W. Neumann, H. Protzmann, M.
Heuken, M. Kneissl, M. Weyers, G. Tränkle
J. Cryst. Growth 310 (23), 4932 (2008)
17. Growth and characterization of manganese-doped InAsP
M. Pristovsek, Ch. Meißner, and M. Kneissl, R. Jakomin, S. Vantaggio, and T.
Tarricone
J. Cryst. Growth 310, 5028 (2008)
18.* Ripening of InAs Quantum Dots on GaAs (001) investigated with in-situ Scanning
Tunneling Microscopy in Metal-Organic Vapor Phase Epitaxy
Raimund Kremzow, M. Pristovsek, M. Kneissl
J. Cryst. Growth 310, 4751 (2008)
19.* The critical thickness of InGaN on (0001) GaN
Martin Leyer, Joachim Stellmach, Christian Meissner, Markus Pristovsek, Michael
Kneissl
J. Cryst. Growth 310, 4913 (2008)
20. Ultraviolet light-emitting diodes promise new solutions for water purification
Michael Kneissl
World Water & Environmental Engineering, Vol. 31 (3), 35 (2008)
21. Structural and optical properties of non-polar GaN thin films
Z. H. Wu, A. M. Fischer, F. A. Ponce, B. Bastek, J. Christen, T. Wernicke, M. Weyers,
M. Kneissl
Appl. Phys. Lett. 92, 171904 (2008)
155
22.* A-plane GaN ELO structures: growth domains, morphological defects, and
impurity incorporation directly imaged by scanning cathodoluminescence
microscopy
B. Bastek, F. Bertram, J. Christen, T. Wernicke, M. Weyers, M. Kneissl
Appl. Phys. Lett. 92, 212111 (2008)
23.* Effect of the barrier composition on the polarization fields in near UV InGaN light
emitting diodes
A. Knauer, H. Wenzel, T. Kolbe, S. Einfeldt, M. Weyers, M. Kneissl, G. Tränkle
Appl. Phys. Lett. 92, 191912 (2008)*
24.* Indium Nitride Quantum Dot growth modes in Metal-Organic Vapour Phase
Epitaxy
Christian Meissner, Simon Ploch, Martin Leyer, Markus Pristovsek and Michael Kneissl
J. Cryst. Growth 310, 4959 (2008)
25. Microstructure of a-plane (2-1-10) GaN ELOG stripe patterns with different inplane orientation
Tim Wernicke, Ute Zeimer, Martin Herms, Markus Weyers, M. Kneissl, Gert Irmer
Journal of Materials Science: Materials in Electronics (2008), DOI 10.1007/s10854-0089638-9
26. Anisotropic strain on phonons in a-plane GaN layers studied by Raman scattering
G. Irmer, T. Brumme, M. Herms, T. Wernicke, M. Kneissl, M. Weyers
Journal of Materials Science: Materials in Electronics (2008) DOI 10.1007/s10854-0079557-1
27.* High-temperature growth of AlN in a Production Scale 11x2” MOVPE reactor
F. Brunner, H. Protzmann, M. Heuken, A. Knauer, M. Weyers, and M. Kneissl
phys. stat. sol. (c), 1 (2008)
28. Wavelength and intensity switching in directly coupled semiconductor microdisk
lasers
Gustavo E. Fernandes, Laurent Guyot, Grace D. Chern, Michael Kneissl, Noble M.
Johnson, QingHai Song, Lei Xu, and Richard K. Chang
Optics Letters 33, 605 (2008)
29.* Semipolar GaN grown on m-plane sapphire using MOVPE
Tim Wernicke, Carsten Netzel, Markus Weyers, Michael Kneissl
phys. stat. sol. (c) 5, 1815 (2008)
30. Near band edge and defect emissions from epitaxial lateral overgrown a-plane GaN
with different stripe orientations
C. Netzel, T. Wernicke, U. Zeimer, F. Brunner, M. Weyers, and M. Kneissl
J. Cryst. Growth 310, 8 (2008)
31. In-situ monitoring for nano-structure growth in MOVPE
Markus Pristovsek, Wolfgang Richter
in Semiconductor Nanostructures, Ed. by D. Bimberg,
Springer Berlin-Heidelberg-New York (2008) , Chapter 3, 67-86
32. Volmer-Weber growth mode on InN quantum dots on GaN by MOVPE
Christian Meissner, Simon Ploch, Markus Pristovsek, Michael Kneissl
phys. stat .sol. (c) (2008), in print
156
33. Shape of InN Quantum Dots and Nanostructures grown by Metal Organic Vapour
Phase Epitaxy
S. Ploch, C. Meissner, M. Leyer, M. Pristovsek, M. Kneissl
phys. stat .sol. (c), 1– 4 (2009) / DOI 10.1002/pssc.200880938
34. Critical Thickness of InGaN
M. Pristovsek, M. Leyer, J. Stellmach, C. Meißner, M. Kneissl
phys. stat .sol. (c) (2008), in print
35. Bonding configuration of cyclopentene on InP(001)(2x4) surface
Regina Paßmann, Priscila Favero, Wolf Gero Schmidt, Ronei Miotto Walter Braun ,
Wolfgang Richter,Michael Kneissl, Norbert Esser, Patrick Vogt,
Phys. Rev. B (2008), submitted
36. Strategy of structure analysis of polar and nonpolar GaN layers
W. Neumann, A. Mogilatenko, T. Wernicke, E. Richter, M. Weyers, M. Kneissl
Journal of Microscopy (2008), submitted
37. Adsorption of cyclopentene on GaAs(001) and InP(001), a comparative study by
synchrotron-based core level spectroscopy
R. Paßmann, T. Bruhn, B. O. Fimland, W. Richter, M. Kneissl, N. Esser, P. Vogt,
WSPC (2008), accepted.
38. C=C bonds and their influence on the binding geometry on the on theGaAs(001)c(4
× 4) surface
R. Paßmann, M. Ewald, T. Bruhn, B. O. Fimland, M. Kneissl, N. Esser, P.Vogt
phys. stat .sol. (b) (2009), submitted
39. Growth mode of InGaN on GaN (0001) in MOVPE
M. Pristovsek, J. Stellmach, M. Leyer, M. Kneissl
phys. stat .sol. (c), 1– 5 (2009) / DOI 10.1002/pssc.200880915
40.* Emission characteristics of InGaN multi quantum well light emitting diodes with
differently strained InAlGaN barriers
T. Kolbe, A. Knauer, H. Wenzel, S. Einfeldt, V. Küller, P. Vogt, M. Weyers, M. Kneissl
phys. stat .sol. (c), 1–4 (2009) / DOI 10.1002/pssc.200880895
41. Optimization of InGaN/(In,Al,Ga)N based near UV-LEDs by MQW strain
balancing with in-situ wafer bow sensor
A. Knauer, T. Kolbe, S. Einfeldt, M. Weyers, M. Kneissl, and T. Zettler
phys. stat .sol. (a) 206, 211-214 (2009).
42. Epitaxial Lateral Overgrowth on (2-1-10) a-Plane GaN with [0-111] Oriented
Stripes
T. Wernicke, U. Zeimer, C. Netzel, F. Brunner, A. Knauer, M. Weyers, M. Kneissl
J. Crys. Growth, (2009), doi:10.1016/j.jcrysgro.2009.01.0
43. MOVPE growth for UV-LEDs
A. Knauer, F. Brunner, T. Kolbe V. Küller, H. Rodriguez. S. Einfeldt, M. Weyers and
M. Kneissl
Proc. SPIE 7231, 72310G (2009).
44.
Ultraviolet laser diodes on AlN and sapphire substrates
Michael Kneissl, Zhihong Yang, Mark Teepe, Noble M. Johnson
Proc. SPIE 7230, 7230-13 (2009).
157
9.4.3 Invited talks
Kneissl, Michael
InAlGaN-based UV Light Emitters - Applications and Material
Challenges
Semiconductor and Insulating Materials Conference SIMC-XIV,
Fayettville, USA, May 2007
Kneissl, Michael
Semiconductor-based light emitters in the near and deep UV Status and Challenges, Materials Valley Workshop “Cleaning of
Drinking Water with UV-Radiation”, Hanau, Germany, Feb. 2007
Kneissl, Michael
Deep UV LEDs: Statuts and Challenges,
VDI Meeting "Innovative Beleuchtung mit LED", Düsseldorf,
Deutschland, May 2007
Kneissl, Michael
GaN-based UV light emitter - Applications and Materials
Challenges,
Techneau Workshop, Germany, Sept. 2007
Kneissl, Michael
GaN-basierte LEDs für den ultravioletten Spektralbereich, Beirat
Meeting FBH, Berlin, Germany, Okt. 2007
Kneissl, Michael
Von ultravioletten Leuchtdioden bis zu grünen LasernHerausforderungen und Fortschritte bei der Entwicklung GaNbasierter Lichtemitter,
Seminar at the Fraunhofer Institut für Lasertechnik, Aachen,
Germany, Feb. 2008
Kneissl, Michael
From UV LEDs to green lasers – Challenges and progress in the
development of GaN based light emitters, Seminar HMI, Berlin,
Germany, Feb. 2008,
Kneissl, Michael
The optoelectronic chameleon – GaN-based light emitters from
the UV to green,
DPG Spring Meeting, Berlin, Germany, Feb. 2008
Kneissl, Michael
Nitridhalbleiter: Nanostrukturen für Trinkwasserreinigung und
Laserprojektion,
MONA: Think Tank Innovation of the TU Berlin, Feb. 2008
Kneissl, Michael
GaN Optoelectronic Research in Berlin - Statuts and Qutlook,
Seminar at Palo Alto Research Center , Palo Alto, USA, March 2008
Kneissl, Michael
Von UV LEDs bis zu grünen Lasern - Herausforderungen und
Fortschritte bei der Entwicklung GaN-basierter Lichtemitter,
ZEMI Summer School, Berlin, Sept. 2008
Kneissl, Michael
GaN based laser diodes for the blue and green spectral range,
(Optecc BB) Summer School International, Berlin, Aug. 2008
Kneissl, Michael
InAlGaN-basierte Lichtemitter für das nahe und ferne UV:
Anwendungen und Herausforderungen,
Werkstoffwissenschaftliches Kolloquium, Universität Erlangen, Nov.
2008
158
Pristovsek, Markus
Surface and thin film analysis during vapour phase epitaxial
growth,
13th International Summer School on Crystal Growth, Salt Lake City,
USA, Aug. 2007
Pristovsek, Markus
State of the Art of in-situ Monitoring in Metal Organic Vapour
Phase Epitaxy,
2007 International Seminar, Anan, Japan, Sept. 2007
Pristovsek, Markus
Growth and characterization of manganese-doped InAsP
14th International Conference of Metalorganic Vapor Phase Epitaxy,
Metz, France, June 2008
Pristovsek, Markus
Growth mode of InGaN on GaN (0001) in MOVPE
International Workshop on Nitride semiconductors, Lausannes,
Switzerland, Oct. 2008
Vogt, Patrick
Interface formation between small organic molecules and IIIV(001) surfaces,
Seminar, Liverpool, Großbritannien und Nordirland, Apr. 2007
Vogt, Patrick
Self-assembled films of Lead Phthalocyanine on GaAs(001)
surfaces,
International Seminar at the Universita Tor Vergata, Rome, Italy,
04.2008.
Vogt, Patrick
Bonding con_guration and optical properties of interfaces
between organic molecules and III-V (001) surfaces International
Summershool in Epioptics, Erice Sicily, Italy, 06.2008:
Vogt, Patrick
Molecule-Semiconductor Linkage: From Structure Formation to
Sensors,
ISAS - Institute for analytical Sciences, Dortmund, Germany, Sept.
2008
Vogt, Patrick
Molecule-Semiconductor Interfaces: From Initial Structure
Formation to Technological Application,
Wokshop "Organometallics and Materials Chemistry - a happy
marriage", Berlin, Okt. 2008
159
9.4.4 PhD theses
Roberto Jakomin
MOVPE Growth of InP-Based III-V Compounds Doped with
Transition Metals (Fe, Mn)
Universitá degli studi di Parma, Parma, Italy
26.03.2008
Regina Paßmann
Interface Formation between Hydrocarbon Ring Molecules and
III-V Semiconductor Surfaces
15.08.2008
Mirko Prezioso
Study of electrically active defects in structures with InAs
Quantum Dots in a GaAs matrix
Universitá degli studi di Parma; Parma, Italy
26.03.2008
Sami Suihkonen
Fabrication of InGaN Quantum Wells for LED Application
Helsinki University of Technology, Helsinki, Finland
11.04.2008
Moshe Weizman
Properties of laser-crystallized polycrystalline SiGe thin films
06.06.2008
Stefan Weeke
Segregation of Antimony in InP In MOVPE
30.05.2008
160
161
Tobias Arlt
Ohmsche Kontakte für Halbleitermaterialien auf der Basis von
GaNund ZnO
02.04.2008
Thomas Bruhn
Elektronische Eigenschaften von Grenzflächen zwischen III-VHalbleitern und organischen Ringmolekülen
13.04.2007
Marcel Ewald
Strukturanalyse von molekülterminierten GaAs Oberflächen
16.06.2008
Christian Friedrich
Präparation und atomare Struktur von III-IV
Halbleiteroberflächen
29.11.2007
Matthias Guderian
Nano Strukturentstehung in der MOVPE - Untersuchung mit der
in-situ Rastertunnelmikroskopie
09.05.2008
Tim Kolbe
Analyse der Lumineszens und Strom-Spannungs-Charkteristik
von GaN-basierten Lichtemittern
31.01.2008
Viola Küller
Charakterisierung von GaN-basierten VielfachquantentopfStrukturen für die Emission im ultravioletten Spektralbereich
21.03.2008
Simon Ploch
MOVPE-Wachstum und Charakterisierung von InN basierten
Nanostrukturen
01.02.2008
Vanessa Rackwitz
Untersuchung geordneter Phthalocyanine-Strukturen auf
verschieden rekonstruierten GaAs(001) Oberflächen
26.02.2008
Lars Peter Scheller
Transportuntersuchungen an laserkristallisierten SiliziumGermanium-Legierungen
01.06.2007
Jessica Schlegel
Untersuchung der Emissions- und Gewinncharakteristik
nitridbasierter Laserheterostrukturen
06.09.2008
Joachim Stellmach
Epitaxie und Eigenschaften von InGaN Schichten und
Quantentöpfen
27.03.2008
Marek Warzecha
Strukturelle und optische Charakterisierung von ZnMgO
Schichten
18.08.2008
162
163
9.4.6
Abstracts of selected papers of department IV
2* Appl. Phys. Lett. 90, 101116 (2007)
Influence of quantum-well-barrier composition on gain and threshold
current in AlGaN lasers
W. W. Chow
Semiconductor Material and Device Sciences Department,
Sandia National Laboratories, Albuquerque, New Mexico 87185-1086
M. Kneissl
Institut of Solid State Physics, Technische Universitat Berlin, Hardenbergstrasse 36,
J. E. Northrup and N. M. Johnson
Electronic Materials and Devices Laboratory, Palo Alto Research Center,
3333 Coyote Hill Road, Palo Alto, California 94304
In an AlGaN quantum-well laser, the presence of Al affects the optical properties of the gaingenerating active region partly because of the distinct difference in the band structure between
AlN and GaN or InN. The intricate connection between band structure and internal-electricfield effects leads to a noticeably stronger influence of barrier composition on optical gain,
lasing polarization, and threshold current than in conventional near-infrared III-V lasers.
4* J. Appl. Phys. 101, 123103 (2007)
Ultraviolet semiconductor laser diodes on bulk AlN
Michael Kneissl, Zhihong Yang, Mark Teepe, Cliff Knollenberg, Oliver Schmidt,
Peter Kiesel, and Noble M. Johnson
Palo Alto Research Center, Inc., 3333 Coyote Hill Road, Palo Alto, California 94304
Sandra Schujman and Leo J. Schowalter
Crystal IS, Incorporated, 70 Cohoes Avenue, Green Island, New York 12183
Current-injection ultraviolet lasers are demonstrated on low-dislocation-density bulk AlN
substrates. The AlGaInN heterostructures were grown by metal organic chemical vapor
deposition. Requisite smooth surface morphologies were obtained by growing on near-c-plane
AlN substrates, with a nominal off-axis orientation of less than 0.5 degree. Lasing was
obtained from gain-guided laser diodes with uncoated facets and cavity lengths ranging from
200 m to 1500 m. Threshold current densities as low as 13 kA/cm2 were achieved for
laser emission wavelengths as short as 368 nm, under pulsed operation. The maximum light
output power was near 300 mW with a differential quantum efficiency of 6.7%. This (first)
demonstration of nitride laser diodes on bulk AlN substrates suggests the feasibility of using
such substrates to realize nitride laser diodes emitting from the near to deep ultraviolet
spectral regions.
164
14* J. Cryst. Growth 310, 4525 (2008)
Influence of MOVPE growth temperature on the structural and optical
properties of InGaN MQW laser diodes
V. Hoffmanna, A. Knauera, F. Brunnera, C. Netzela, U. Zeimera, S. Einfeldta, M. Weyersa, G.
Tränklea, J.M. Karaliunasb, K. Kazlauskasb, S. Jursenasb, U. Jahnc, J.R. van Lookd and M.
Kneissla,d
a
Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, D-12489
Berlin, Germany
b
Institute of Materials Science and Applied Research, Vilnius University, LT-10222 Vilnius,
Lithuania
c
Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
d
Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstraße 36, 10623
Berlin, Germany
The morphological and optical properties of InGaN multiple quantum wells (MQWs) emitting
at 405 nm are studied with respect to the MQW growth temperature. The latter was varied
between 760 and 840 °C in structures grown on c-plane sapphire substrates by metal-organic
vapor-phase epitaxy (MOVPE). The indium content in the quantum well was kept constant
for all temperatures by adjusting the trimethylindium supply. The MQWs were inserted as
active region in both optically pumped laser heterostructures and laser diodes (LDs). We
found that low growth temperatures result in a reduced spatial uniformity of the luminescence
emission wavelength due to well thickness variations, whereas at higher temperatures it is
difficult to obtain a spatially homogeneous indium concentration. A minimum threshold
power density for optically pumped lasing was found for growth temperatures of the active
region between 780 and 820 °C. LDs with an MQW grown at these conditions showed an
onset of lasing at a current density of 6.5 kA/cm2 with output powers of more than 350 mW.
18* J. Cryst. Growth 310, 4751 (2008)
Ripening of InAs quantum dots on GaAs (0 0 1) investigated with in situ
scanning tunneling microscopy in metal–organic vapor phase epitaxy
Raimund Kremzow, Markus Pristovsek and Michael Kneissl
Berlin, Germany
We report on the first in situ scanning tunneling microscopy (STM) measurements showing
Ostwald ripening of InAs quantum dots (QDs) grown on Si-doped (0 0 1) GaAs by metal–
organic vapor phase epitaxy (MOVPE). During an annealing step in the reactor under arsenic
overpressure immediately after QD growth at
the change in QD density and size
distribution could be observed directly in a sequence of in situ STM images over 50 min. The
density of the InAs QDs decreases reciprocally during the annealing step, which agrees well
with Ostwald ripening limited by indium attachment/detachment.
165
19* J. Cryst. Growth 310, 4913 (2008)
The critical thickness of InGaN on (0 0 0 1)GaN
M. Leyera, J. Stellmacha, Ch. Meissnera, b, M. Pristovseka and M. Kneissla
a
Technische Universität Berlin, EW 6-1, Institut für Festkörperphysik, Hardenbergstraße 36,
D-10623 Berlin, Germany
b
ISAS - Institute for Analytical Sciences, Albert-Einstein-Straße 9, 12489 Berlin, Germany
The critical thickness for the relaxation of InGaN layers grown on (0 0 0 1)GaN on sapphire
for an indium content between 10% and 20% has been determined experimentally. The layers
were grown by metal-organic vapour phase epitaxy (MOVPE). The indium content was
varied by changing growth temperature between 700 and 750 °C. In-situ ellipsometry could
identify a growth mode transition during layer growth, from relatively smooth InGaN layer to
a rougher layer with higher indium content. X-ray diffraction found a completely strained
layer with lower indium content and a completely relaxed layer with higher indium content.
These findings were consistent with absorption and photoluminescence measurements.
22* Appl. Phys. Lett. 92, 212111 (2008)
A-plane GaN epitaxial lateral overgrowth structures: Growth domains,
morphological defects, and impurity incorporation directly imaged by
cathodoluminescence microscopy
B. Bastek,1 F. Bertram,1 J. Christen,1 T. Wernicke,2 M. Weyers,2 and M. Kneissl2,3
1
Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, P.O. Box 4120,
39160 Magdeburg, Germany
2
Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhof-Staße 4, 12489
Berlin, Germany
3
Institute for Solid State Physics, Technical University Berlin, Berlin, Hardenbergstraße 36,
The distinctly different growth domains of a-plane epitaxial lateral overgrown GaN on stripe
masks oriented along [01 0] direction were directly visualized by highly spatially and
spectrally resolved cathodoluminescence microscopy. Clear cut microscopic regions
dominated by differing individual peak wavelengths originating from either basal plane
stacking faults, prismatic stacking faults, impurity related donor-acceptor pair or (D0,X)
emission are explicitly correlated to the different growth domains. The luminescence in the
domains grown in [0001] direction over the mask [epitaxial lateral overgrown wings] is
dominated by the intense and sharp (D0,X) emission at 3.471 eV. Here, no luminescence
originating from morphological defects is found over several micrometers. This evidences the
excellent material quality of the a-plane GaN, which is fully relaxed at the surface of the
wings. ©2008 American Institute of Physics
166
23* Appl. Phys. Lett. 92, 191912 (2008)
Effect of the barrier composition on the polarization fields in near UV
InGaN light emitting diodes
A. Knauer,1 H. Wenzel,1 T. Kolbe,2 S. Einfeldt,1 M. Weyers,1 M. Kneissl,1,2 and G. Tränkle1
1
Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchoff-Straße 4,
2Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstr. 36,
The electroluminescence from near ultraviolet (UV) light emitting diodes containing InGaN
multiple quantum wells (MQWs) with GaN, AlGaN, and InAlGaN barriers was investigated.
Based on band-structure calculations the observed wavelength shift in the peak emission with
increasing injection current is attributed to the screening of the polarization fields and to band
gap renormalization. InGaN MQWs with almost zero net polarization have been realized. No
blueshift in the emission spectra of these devices was observed over the entire current range.
24* J. Cryst. Growth 310, 4959 (2008)
Indium nitride quantum dot growth modes in metalorganic vapour phase
epitaxy
Christian Meissnera, b, Simon Plocha, Martin Leyera, Markus Pristovseka and Michael
Kneissla
a
Institut für Festkörperphysik, Technische Universität Berlin, EW 6-1,
b
ISAS - Institute for Analytical Sciences, Albert-Einstein-Straße 9, 12489 Berlin,
Germany
We have investigated growth of InN quantum dots (QDs) on GaN (0 0 0 1) in metalorganic
vapour phase epitaxy as a function of growth temperature, trimethylindium partial pressure,
and growth time. The growth was analysed in situ by spectroscopic ellipsometry and ex situ
by X-ray diffraction and atomic force microscopy. The QDs were found for all growth
temperatures between 480 °C and 600 °C and for all growth times. The density increased
exponentially with decreasing growth temperature, up to
for 500 °C. By changing the
amount of deposited material it was possible to control the size of the QDs. Above 530 °C a
reduction of the effective growth rate was also observed. Reducing the V/III ratio by
trimethylindium partial pressure from 15,000 to 5000 led to an increase in the growth rate.
Both effects are due to reduced etching of the InN QDs by ammonia.
167
27* p hys. stat. sol. (c) 5, No. 6, 1799 (2008)
High-temperature growth of AlN in a production scale 11x2” MOVPE
reactor
F. Brunner1, H. Protzmann2, M. Heuken2, A. Knauer1, M. Weyers1, and M. Kneissl1
1
Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin,
Germany
2
AIXTRON AG, Kackertstr. 15-17, 52072 Aachen, Germany
We report on the growth of high quality AlN films on sapphire by MOVPE in an
AIX2400G3-HT planetary reactor. Specific reactor hardware modifications were conducted to
facilitate growth temperatures of up to 1600 °C and to obtain reduced parasitic gas phase
reactions. Growth was optimized regarding growth rate and surface morphology as well as
optical and structural properties of the AlN layers on sapphire. With increasing growth
temperature we observe a transition from an AlN surface with a high density of large pits to a
smooth pit-free morphology. The improvement in material quality with growth temperature is
confirmed by X-ray diffraction, AFM, SIMS and Raman measurements. The impact of
residual or intentionally introduced Ga during growth on AlN material properties is discussed
29* phys. stat. sol. (c) 5, No. 6, 1815 (2008)
Semipolar GaN grown on m-plane sapphire using MOVPE
Tim Wernicke1, Carsten Netzel1, Markus Weyers1, and Michael Kneissl1,2
1
2
Ferdinand-Braun-Institut für Höchstfrequenztechnik, Berlin, Germany
Institute of Solid State Physics, Technical University of Berlin, Berlin, Germany
We have investigated the MOVPE growth of semipolar gallium nitride (GaN) films on (10 0)
m-plane sapphire substrates. Specular GaN films with a RMS roughness (10 × 10 m2) of
15.2 nm were obtained and an arrowhead like structure aligned along [ 113] is prevailing. The
orientation relationship was determined by XRD and yielded (2 2)GaN (10 0)sapphire and [
113]GaN [0001]sapphire as well as [ 113]GaN [000 ]sapphire.PL spectra exhibited near band
edge emission accompanied by a strong basal plane stacking fault emission. In addition lower
energy peaks attributed to prismatic plane stacking faults and donor acceptor pair emission
appeared in the spectrum. With similar growth conditions also (10 ) GaN films on m-plane
sapphire were obtained. In the later case we found that the layer was twinned, crystallites with
168
40* Phys. Status Solidi C, 1–4 (2009) / DOI 10.1002/pssc.200880895
Emission characteristics of InGaN multi quantum well light emitting diodes
with differently strained InAlGaN barriers
T. Kolbe1, A. Knauer2, H. Wenzel2, S. Einfeldt2, V. Kueller2, P. Vogt1, M. Weyers2, and M.
Kneissl1,2
1
Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstraße 36, 10623
Berlin, Germany
2
Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489
Berlin, Germany
In this paper we report on the emission characteristics of InGaN multi quantum well light
emitting diodes (LEDs) in the near ultra-violet (UV) spectral range. GaN, AlGaN and
InAlGaN with various indium contents were compared as barrier material in the InGaN
quantum well active region of the device heterostructure. It was found that the emission
wavelength decreases with increasing drive current. This blue shift with an increasing indium
content in the quaternary barriers can be attributed to the screening of the polarization fields
and band gap renormalization. Light emitting diodes with a constant emission wavelength
over a wide current range were realized by using nearly lattice matched InAlGaN barriers.
These devices also showed the highest light output power even though the band offset
between the quantum wells and the barriers is smaller in comparison to the LEDs with the
AlGaN barriers. These effects can be explained by the interplay of a reduction defect density
at the quantum well/barrier interface and a improved overlap of the electron and hole wave
functions due to the reduction of quantum confined Stark effect.
Transparent Ring
Interconnection Using
Multiwavelength PHotonic
Nano-Photonics Materials
and Technologies for
Multicolor High-Power
Sources
switches
VS
Halbleiter - Nanophotonik
SFB 787
Arbeitsgemeinschaft der
Nanotechnologie-Kompetenzzentren
Deutschlands

Institute of Solid State Physics Institut für Festkörperphysik 2007-2008

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