The history of the WSI
The Walter Schottky Institut (WSI) is a central institute of Technische Universität München (TUM) that was founded in order to strengthen the interaction between basic physics and semiconductor electronics research. The idea to create such an interdisciplinary research facility first emerged in the early 1980’s. Semiconductor heterostructures had become a very popular field of research at that time following the discoveries of many novel electronic and optical effects in low dimensional systems such as two-dimensional electron gases and quantum wells. The most prominent discoveries in semiconductor physics were the Quantum Hall Effect by Klaus von Klitzing in 1980 (Nobel prize 1985) and the Fractional Quantum Hall Effect by Daniel Tsui, Horst Störmer and Arthur Gossard in 1982 (Nobel prize for Tsui, Störmer and Laughlin (theory) in 1998). At the same time various technologically relevant novel electronic and optical devices were proposed and developed. Specific examples include Quantum Well Lasers (Henry, Dingle, Holonyak, Tsang and others), Resonant Tunnelling Diodes (Esaki, Tsu, Chang and others), or High Electron Mobility Transistors (Abstreiter, Ploog, Mimura and others). These devices provided new functionality and led to a wide variety of applications for example in the field of communication technology (satellite receivers, optical communication, cellular phones). The achievements were based on the excellent materials control through epitaxial techniques, especially molecular beam epitaxy. These modern materials technologies allowed control of layered structures on an atomic scale and were widely employed in industrial laboratories in United States and Japan as basis for the realization of novel devices. In Munich, this kind of research and development was embedded in a collaborative research center funded by the German Research Association (SFB 128 “Elementare Anregungen an Oberflächen”), where in one research area two-dimensional electron systems at semiconductor interfaces were studied. This work was concentrated at the chair of Fred Koch at the Physics Department of TUM and the project leaders in the early eighties were Fred Koch, Klaus von Klitzing and Gerhard Abstreiter. Around the same time closer interactions developed between the TUM physics groups and the research and development center of Siemens AG in the area of microstructured devices. In addition, a joint research program funded by Volkswagenstiftung was established between Gerhard Abstreiter and Klaus von Klitzing of E16 with Erich Gornik’s group at the University of Innsbruck. The successful projects were strongly dependent on high quality materials which were provided by only a very few sources; namely Günter Weimann from the research laboratory of Deutsche Bundespost in Darmstadt and Klaus Ploog from Max-Planck-Institut Stuttgart. At the time, these two laboratories were the only groups in Germany which could grow high quality GaAs based heterostructures. There was a strong need for an interdisciplinary research environment that combined high quality semiconductor hetero- and nanomaterials technology with basic physics as well as device development.
Fig. 1: Meeting to discuss the establishment of a institute for semiconductor and microelectronic research.
In February 1985, Gerhard Abstreiter wrote a memorandum with the suggestion to create a new institute with a specific focus on semiconductor micromaterials research and device development. This proposal was discussed with Karl-Heinz Beckurts, who at that time was head of the Siemens research laboratories and had already expressed strong interest in strengthening collaborations between industry and the TUM. In September 1985 the proposal received additional impetus after it was announced that Klaus von Klitzing would receive the Nobel Prize in Physics for his discovery of the Quantum Hall Effect. Klaus von Klitzing had just left the Physics Department of TUM in early 1985 to take up a directorship at Max-Planck-Institut für Festkörperforschung in Stuttgart. The Nobel Prize had an extremely positive impact on the initiative for the realization of a new research facility at TUM and both Fred Koch and Wilhelm Brenig, at that time dean of the physics department of TUM, wrote supporting letters in October / November 2005 suggesting the creation of a research institute focusing on semiconductor physics and electronics. The name “Walter Schottky Institut” was suggested by Karl-Heinz Beckurts in a meeting at the Physics Department in Garching. Walter Schottky was a famous and well known physicist who worked for Siemens from 1927 until 1976 when he died close to his 90th birthday. His research combined basic physics with development of novel devices. The combination of materials technology, fundamental physics and device applications was planned to become the central mission and principle goal of the new institute. The idea to create such a research facility was strongly supported by Klaus von Klitzing and Wolfgang Wild, president of TUM and later Bavarian Minister for Science, Research and Art.
Fig. 2: A vision becomes reality – architects model the Walter Schottky Institute.
Already on December 17, 1985, there was a meeting at the Bayerische Staatsministerium für Unterricht und Kultus with Bavarian State Minister Hans Maier to discuss the boundary conditions for the foundation of a research institute for semiconductor electronics at TUM in collaboration with Siemens AG (figure 1). Following an additional meeting of Klaus von Klitzing with Bavarian’s Minister President Franz Josef Strauß in February 1986 the final decision to create such an interdisciplinary research institute was made. It was the year of the hundredth birthday of Walter Schottky. From then on it took only about two years until the new laboratories became operational in 1988 (figure 2).
Fig. 3: Inauguration ceremony on July 14th, 1988.
Research in the new institute started in May, a few months before the official inauguration and opening ceremony on July 14th, 1988 (figure 3). This exceptionally short time for planning and construction of a modern institute building was made possible by the excellent cooperation between the Siemens AG, the Bavarian ministries and the TUM. Interests of university, industry and politics met here in a rare but fortunate circumstance. The realization of the WSI was based on an official TUM-Siemens collaboration effort called “Sonderforschungseinheit mikrostrukturierte Bauelemente”. As discussed already in the foreword, it was the first example where industry took the responsibility for the construction of a laboratory building at TUM. Many people were particularly helpful in setting up the new research institute: The strong commitment of Karl-Heinz Beckurts was essential for the whole project. In the early planning stage he became victim of a terrible bomb attack by terrorists belonging to the Rote Armee Fraktion (RAF) where he and his chauffeur were murdered. It is extremely sad and regrettable that he was no longer amongst us at the official opening of the WSI in summer 1988 (figure 3).
About the Walter Schottky Institut
- The WSI building contains laboratories and offices with a total area of about 2400 m². The heart of the institute is a 250 m² clean room facility for state-of-the-art semiconductor technology. The costs for the building (16,4 million DM) were initially covered by Siemens. TUM bought the institute in 1992. The Bavarian State gave generous funding for the initial equipment (15 million DM) and created three new full professorships, with a total of 23 staff positions, one chair belonging to the department of electrical engineering and information sciences and two to the physics department. Further support came from the Institute of Theoretical Physics of TUM, which in 1990 devoted one chair to theoretical semiconductor physics in order to provide theoretical support for the WSI. The following research groups were established:
- Semiconductor technology: Günter Weimann (from 1988 to 1995), Markus-Christian Amann (since 1997)
- Experimental semiconductor physics I: Gerhard Abstreiter (since 1987)
- Experimental semiconductor physics II: Erich Gornik (from 1988 to 1993), Martin Stutzmann (since 1993)
- Theoretical semiconductor physics: Peter Vogl (since 1990)
The main research interests have been:
- Fabrication and characterization of new semiconductor materials, material combinations, as well as functionalisation of surfaces
- Development of novel methods for fabrication and characterization of nanostructures
- Basic physics with emphasis on electronic and optical properties of low dimensional systems
- Realisation of new semiconductor devices for applications in ultrafast electronics, optoelectronics, and as biological / chemical sensors
- Theory and simulation of modern semiconductor materials and devices
The early projects concentrated on Si , GaAs, and InP based systems, with emphasis on heteroepitaxy on an atomic scale. Device oriented projects have been the development of ultrafast and low-noise III-V hetero-field-effect-transistors, laser diodes in the wavelength range from 980 nm to 1.55µm, vertical emitting laser diodes and Si / SiGe based devices. Fundamental research projects involved optical studies of quantum wires and dots, especially spatially resolved spectroscopy, transport and resonant tunnelling in low dimensional systems, as well as the realization of novel devices based on quantum-effects. More recently, interest have shifted also towards other newly emerging materials such as GaN and related alloys, diamond, or Antimonides and towards quantum control of charges, spins and photons for quantum information technology. In addition, the combination of semiconductors with biological systems was started a couple of years ago. This new field of research opens novel biomedical applications, e.g. for diagnostics and sensing.
Soon after its foundation, the Walter Schottky Institut became an internationally well-known landmark for fabrication and characterization of high quality semiconductor hetero- and nanostructures. This was the basis for many national and international collaborations (see chapter 143). The WSI played a key role in establishing various collaborative research centers funded by German Research Association as well as national research programs supported by the federal ministry of research. Other funding was obtained from Bayerische Forschungsstiftung, Volkswagenstiftung, European Union and industry. The total amount of annual external funding is on the average more than 3 million Euros per year. The various national and international collaborations resulted in many joint publications in refereed international journals. The total number of publications with contributions from the WSI is about 1600 which have been cited about 27000 times up to now (at present about 2500 citations per year) according to ISI Web of Science (June 2008). About 350 diploma (master) students have graduated from the WSI until now. In the same period, 130 doctorate candidates have finished their theses. All of the students were able to find appropriate jobs in a very short time after finishing their thesis. About 70% of the PhDs are now working for high-tech industry. Twenty percent remained in academia and one third of those are now professors at other universities or directors of research institutes. 10% went into other areas like patent business or consulting.
The number of researchers at the Walter Schottky Institut has grown continuously. Today it accommodates the research groups headed by Gerhard Abstreiter, Markus-Christian Amann, Martin Brandt, Anna Fontcuberta i Morral, Jonathan J. Finley, Alexander Holleitner, Martin Stutzmann, and Peter Vogl, with a total headcount of about 140, including junior research group leaders, scientific and technical staff, postdocs and visiting researchers, secretaries, and doctorate as well as diploma (master) students. Out of these, about 30 positions are funded by TUM, while basically all the doctorate positions are financed via research projects with external funding. Available laboratory and office space is by far not sufficient anymore and the WSI urgently needs an expansion. A new Center for Nanotechnology and Nanomaterials is currently in the planning stage and it is expected that this shared facility will become operational in fall 2010.
In addition to their extensive research activities, all groups are involved in teaching within their respective departments. Besides the usual teaching responsibilities in undergraduate and graduate courses, special emphasis is put on the education of diploma and doctoral students in the physics and technology of present and future nano-devices and of low dimensional semiconductor structures.