Kurzfassung
Abstract
Acknowledgment
List of Chemical Formulae
List of Symbols
1  Introduction
 1.1  Introduction: gallium nitride and related alloys (III-nitrides)
 1.2  GaN applications and characteristics
 1.3  Physical properties of III-nitrides
  1.3.1  Crystal structure
  1.3.2  Mechanical properties
  1.3.3  Hetero-epitaxial relations with substrates
 1.4  Defects in III-nitrides
  1.4.1  Dislocations
 1.5  Outline of the thesis
2  Elements of elasticity theory
 2.1  Introduction
 2.2  Fundamental equations
  2.2.1  Matrix notation
 2.3  Transformations
3  Dislocation energy
 3.1  Introduction
 3.2  Dislocation energy
 3.3  Dislocation in an isotropic continuum
 3.4  Dislocation in an anisotropic continuum
 3.5  Pre-logarithmic coefficients
 3.6  Comparison of pre-logarithmic terms based on a continuum and atomistic approach
 3.7  Dislocation configurations
  3.7.1  Dislocation types in the bulk
  3.7.2  Dislocation types near the free surface
 3.8  Summary
4  Critical Thickness
 4.1  Introduction
 4.2  The critical thickness criterion
  4.2.1  Work done by the misfit strain
  4.2.2  Dislocation energy
  4.2.3  A straight dislocation at the interface of anisotropic materials
  4.2.4  The critical thickness models
 4.3  Impact of the anisotropy on the critical thickness criterion
 4.4  The critical thickness according to Willis, Jain and Bullough
 4.5  Overall comparison of various effects on the predicted critical thickness
 4.6  Comparison between theoretical and experimental critical thicknesses
 4.7  Summary
5  Reduction of the threading dislocation density
 5.1  Introduction
 5.2  Mathis Model
  5.2.1  Application to semipolar GaN
 5.3  Misfit dislocation density
  5.3.1  Application to AlGaN film on AlN substrate
 5.4  Threading dislocation density in heterostructures
  5.4.1  Motion of an isolated TD
  5.4.2  Reactions among dislocations
  5.4.3  Sessile and glissile dislocations
  5.4.4  Initial and boundary conditions
  5.4.5  GaN/AlN bilayer
  5.4.6  GaN-based multilayer
 5.5  Summary
6  Conclusions and outlook