Semiconductor Physics

This module provides an introduction to the structural, electronic and optical properties of modern semiconductor materials and their associated nanostructures. The scientific and economical importance of semiconductor physics as a cross-cutting part of modern solid state physics is briefly outlined. Then, an introduction to the different methods for the fabrication and deposition used for ultrapure semiconductor materials, alloys and mixed crystal "multi-layer" systems will be given. The main body of the module deals with material and electronic properties of the most commonly used semiconductors. In particular, the electronic bandstructure and the resulting properties of effective mass electrons, holes and other relevant quasiparticles such as excitons are discussed. Equilibrium charge carrier statistics in intrinsic (undoped) semiconductors are then explored before discussing how doping can be used to controllably modify the electronic properties. This is followed by a discussion of electronic properties of semiconductors under application-related non-equilibrium conditions, such as illumination in solar cells or photo-detectors, or voltage biasing in diodes or transistors. To this end, the basic properties  of semiconductor/semiconductor-, semiconductor/metal-, and semiconductor/insulator-hetero-interfaces will be introduced.

After participation in the Module the student is able to:

1. Describe the crystal structure and explain the principle fabrication methods for the most prominent semiconductor materials
2. Explain and calculate the electronic bandstructure of these materials and its dependence on material composition.
3. Understand the terms "two-dimensional", "one-dimensional" and "zero-dimensional" semiconductor nanostructure and explain the influence of quantum confinement on the electronic properties of semiconductors.
4. Understand and explain the physics of charge carrier statistics and scattering governing electrical conductivity in bulk semiconductors and low dimensional nanostructures.
5. Understand and explain the optical properties of semiconductors, in particular optical absorption and recombination of non-equilibrium charge carriers.
6. Understand and explain the basic properties of semiconductor surfaces and interfaces with device-relevant applications to Schottky diodes, solar cells and heterojunctions in optoelectronivs.

No preconditions in addition to the requirements for the Master’s program in Physics.

The modul consists of a lecture and exercise classes.

A written manuscript developped on a tablet PC and projected during the lecture. Additional power point presentations summarizing complicated details and state-of-the-art research results. An excercise is offered for the students to obtain a better comprehension of the lecture contents and to improve their familiarity with them.

Power point and One Note presentation.

Standard textbooks of semiconductor physics, e.g.:

• Fundamentals of Semiconductors, P.Y. Wu, M. Cardona, Springer 2006:
  Schwerpunkt auf Theorie, hohes Niveau, viel Optik
• Physics of Semiconductors, Marius Grundmann, Springer 2006:
  Mehr Anwendungs- und Materialbezug
• Semiconductor Physics and Applications, M. Balkanski, R.F. Wallis, Oxford University Press 2000: 
  Gute Übersicht über derzeitigen Stand, inklusive theoretische Konzepte und Bauelemente
• Halbleiterphysik, R. Sauer, Oldenburg, 2009:
  derzeit einziges empfehlenswertes deutschsprachiges Lehrbuch
• Semiconductor Material and Device Characterization, D. K. Schröder, Wiley-IEEE 2006:
  viele Methoden der Halbleiterphysik

There will be a written exam of 90 minutes duration. Therein the achievement of the competencies given in section learning outcome is tested exemplarily at least to the given cognition level using calculation problems and comprehension questions.

For example an assignment in the exam might be:

• Describe the structure of the Silicon valence band around k=0 based on tight binding theory.
• How do the effective masses of a semiconductor close to the band extrema scale with the band gap?
• Determine the position of the Fermi level in undoped silicon at T=20K and T=400K
• Calculate the reverse bias leakage current density of an ideal Schottky barrier with barrier height 1 eV for a reverse bias of 3V at T=20K and T=400K.

Participation in the exercise classes is strongly recommended since the exercises prepare for the problems of the exam and rehearse the specific competencies.