Research activities - Introduction

Semiconductor physics, being one of the largest branches of solid state physics, studies both the fundamental principles of nature and the complexity of its systems. Semiconductors reflect the enormous diversity in phenomena and complexity in nature more vividly than most other physical systems. Clearly, semiconductors form the heart of modern technology, as every chip and every laser in any high tech gadget is made out of them. What renders semiconductors really unique and fascinating, however, is their incredible richness in phenomena, and the enormous range of their physical parameters.

Where, do you think, can we study atoms in extreme conditions that naturally only occur in neutron stars? Where, do you believe, can we watch free quarks - a breakup of the fundamental electrical charge? In semiconductors! In fact, recently Horst Störmer was awarded the nobel prize for finding free fractional charges in a semiconductor called Galliumarsenide. The physical properties of semiconductors can be tailored and adjusted by so many orders of magnitude, its "building blocks" - the atoms - can be arranged one by one at will, so that they help us forming a whole new world in the lab - artificial atoms with the shape of a square box, artificial molecules a thousand times larger than natural ones so we can inspect their properties easily, long wires with just a single atom's diameter, nanosized machines that may perhaps travel our blood vessels one day, and so on and so on.

We at the Walter Schottky Institut use simple table top experiments as well as large and highly sophisticated equipment, rigorous mathematical theory and phenomenological theory, analytic formalism and computer simulation. All these approaches meet in semiconductor physics, frequently within a single doctoral thesis.

Research activities - Funding

The WSI is well funded by several national and international research agencies and industries and equipped with state of the art fabrication and characterization tools for semiconductors that put its laboratories at the forefront of international semiconductor research. A list of the most prominent funding partners is available here

Research activities - Details

The research activity of the WSI thus covers a wide spectrum from basic physics in low-dimensional semiconductor structures to the development of novel or improved electronic and optoelectronic devices based on semiconductor heterostructures. The close collaboration between the different groups and the availability of various experimental techniques are the essential basis for the successful development of novel semiconductor devices. Close contacts with industrial partners, especially with Infineon Corporation (formerly Siemens) have also proven to be very fruitful and stimulating in picking up new ideas and in following new directions which may be relevant for future applications.

Apart from the 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 modern and future devices and of low-dimensional semiconductor structures.

E24: Experimental Semiconductor Physics I (Gerhard Abstreiter)

Research projects of E24 deal with various aspects of electronic and optical properties of low-dimensional, mesoscopic semiconductor structures, the heteroepitaxy of group IV and III-V semiconductors, the development of novel methods for lateral patterning and self assembly of quantum wires and quantum dots, the use of various analytical tools for the characterization of nanometer-sized structures in collaboration with external groups, as well as the fabrication and test of new, unconventional electronic and optoelectronic devices. Examples for basic research are optical spectroscopy of single quantum dots, cleaved edge overgrowth on GaAs, magnetotransport in ultrahigh mobility GaAs heterostructures as well as electronic transport and tunneling in edge channels and one-dimensional systems. Device and technology oriented work aims at novel concepts for charge and spin storage in quantum dots, coherent devices based on quantum dots for future quantum information technology, photonic crystal microcavities for efficient single photon sources and the test of semiconductor nanostructures for chemical/biological sensors. A new area of research is the controlled manipulation of oligonucleotides on gold surface for possible protein detection and the development of SOI based lab-on-a-chip systems. Also of increasing interest are carbon based nanostructures and combinations with organic molecules.

Learn more about the different research areas on the research pages of the Abstreiter, Finley, and Holleitner groups.

Major Research Funding

Funding by the following institutions is gratefully acknowledged: 

  Nanosystems Initiative Munich

 TUM Institute for Advanced Study

 Deutsche Forschungsgemeinschaft (Sonderforschungsbereich SFB 631)

Experimental Semiconductor Physics (Martin Stutzmann)

The work of the second semiconductor physics group at the Walter Schottky Institut deals with various aspects of new and non conventional semiconductor materials and material combinations: semiconductors with a wide bandgap (GaN, InGaN, AlGaN, diamond, SiC) disordered semiconductors (amorphous, nanocrystalline, and polycrystalline) advanced thin film systems (silicon-based luminescent layers, thin film solar cells, organic/anorganic heterosystems, biofunctionalized semiconductors). Most of these material systems are prepared in our group by suitable deposition techniques (MBE, MOCVD, Plasma-enhanced CVD, e-beam evaporation, sputtering). Their efficient optimization is based on the large pool of structural, optical, and electrical characterization techniques available in our Institute. Complementary to the usual spectroscopic techniques we have developed and employ a variety of highly sensitive methods which enable us to study in particular the influence of defects on the electronic performance of materials and devices. Such techniques include subgap absorption spectroscopy, optically induced capacitance spectroscopy and, in particular, modern spin resonance techniques which are applied to various materials systems and devices for spintronics.

In addition to the preparation and characterization of new semiconductor materials we also work on the modification and processing of semiconductors with pulsed high power laser systems (laser-crystallization, holographic nano structuring, laser-induced etching) and investigate the potential of new material systems for novel device structures. Recent examples include nano structured thin film solar cells, high electron mobility transistors based on AlGaN/GaN hetero structures, as well as UV-detectors, sensors and biosensors.

Learn more about the different research areas on the research pages of the Stutzmann, Brandt, and Garrido groups.

Semiconductor Technology (Markus-Christian Amann)

Major areas of research are on modern technologies of III-V compound semiconductors, including epitaxy, lithography and etching, and their application in electronic and optoelectronic devices. Molecular beam epitaxy with solid sources (MBE) and gas sources (CBE with group III-alkyls and V-hydrides) is the basis for the controlled growth of heterostructures on GaAs- and InP-substrates for device oriented research, whereas selective growth on masked and patterned substrates is investigated for optoelectronic integration and direct synthesis of one- or quasi zero-dimensional structures of nanometer dimensions. Lateral dimensions in the 100 nm range are obtained by e-beam lithography. Reactive ion etching with high material selectivity and control in monolayer dimensions is utilized for device processing. The device research focuses on key devices, particularly for advanced photonic applications. This includes electronically wavelength tunable lasers, singlemode distributed feedback (DFB) lasers, vertical cavity surface emitting lasers and long wavelength lasers (>1.55 µm) for sensing applications. The development of mathematical models plays an important role for the design and optimization of technological processes and device performance.

The main research projects of E26 are laser devices like Vertical Cavity Surface Emitting Lasers (VCSELs) for sensing applications as well as for high-speed communication systems. For applications in the mid infrared range research on efficient injector less Quantum Cascade Lasers is performed. Furthermore development work in creating single photons in the telecommunications range (1.3µm and 1.5µm) is established.

Theoretical Semiconductor Physics (Peter Vogl)

Semiconductors can be anorganic or organic systems, magnetic or nonmagnetic, highly conducting or insulating, form chains, clusters, cylinders, needles, glasses, or perfectly arranged crystals, their electrons can be arranged to form 2-, 1- or 0-dimensional systems - strange objects that seemed hypothetic a few years ago. Today, however, these structures form the key elements of next generation electronic and optical devices that are being developed world wide. This group develops sophisticated theoretical methods to predict, explain, understand, and control a wide variety of such systems.

Why theory?

How small can a computer, a circuit, a transistor, or a laser be made? Can one design electronic nano-switches that consume no power? How fast can we communicate information inside of a device? How much information can we store on a square nanometer? How do atoms behave when we arrange them in chains, rings, nets, clusters, pyramids, doughnuts? What happens when....

Questions of this kind cannot be answered by making or constructing something. The first step requires a theory and, above all, imagination. The way to proceed is to develop a model that incorporates the physical laws as well as we understand them, focuses on a particular aspect that we feel most essential or promising and work out a possible solution in our mind or in the computer. In our daily work as semiconductor theorists, we design a new material, a new structure, a new device, or we develop a new mathematical or computational method that allows us to tackle complex problems more easily or efficiently. The real fun is to work out predictions that can be checked experimentally.

In most cases, those experiments lead to a lot of surprises, puzzling results that nobody had anticipated. Those surprises are what makes physics so fascinating. Remember that a condensed matter system is a formidably complex system. While we believe to know the basic physical laws that govern the motion of the 1023 electrons and nuclei in a rock, in a semiconductor, as well as in a human being, it is and will always remain an extraordinary challenge to grasp even a tiny bit of the complexity and the vast range of phenomena induced by these many particles.

Are you considering to join us? We do theory in an environment where new experimental data, new materials, new devices pop up all the time and where our predictions can be checked just next door. Why don't you check our areas of research to get a better idea of why theory is not only relevant and fascinating - it is a lot of fun.

TUM Technische Universität München TUM Technische Universität München Physik Department Elektrotechnik und Informationstechnik TUM Technische Universität München
 

Events & News

02 Dec 2014

Graphene layer reads optical information from nanodiamonds electronically   more

22 Nov 2014

Nanoday at the Deutsches Museum !   more

11 Oct 2014

Tag der offenen Tür am Walter Schottky Institut (WSI) und Zentrum für Nanotechnologie und Nanomaterialien (ZNN)   more

24 Sep 2014

International Workshop “Nanoscale Assembly and Transport in Biosystems” October 7th, 2014 Venue: International Graduate School of Science and Engineering (IGSSE)   more

05 Sep 2014

New research group on diamond quantum sensors   more