Modeling of Threading Dislocation Density Reduction in Heteroepitaxial Layers I. Geometry and Crystallography

The geometry of threading dislocations (TDs), non-equilibrium defects that are generated as a r e sult of stress relaxation in thin films, is considered in order to provide a basis for their reduction behavior during heteroepitaxial growth. This paper, the first of a two-part series, discusses the geometric possibility for reactions between TDs as a result of film growth. It is demonstrated that effective TD motion and reaction are responsible for their overall reduction. The reactions become possible if pairs of TDs come within a critical distance: T A for annihilation reactions, TF for fusion reactions, and TS for scattering reactions. The model is used to explain the experimentally observed l / h (h is the film thickness) dependence on TD density. The crystallographic consideration of TDs in the case of (001) growth of f.c.c. semiconductor films is presented and possible reactions between TDs in this case are analyzed.