Dislocation formation and glide in atomically-ordered III-V semiconductors

Abstract

Strain relaxation of III-V materials is a complex process that can be heavily influenced by material microstructure. In this thesis, I investigate the effects of CuPt atomic ordering on dislocation formation and glide in III-V materials. CuPt atomic ordering has been observed in many ternary and quaternary III-V materials, and consists of alternating {111} planes of one or both of the mixed-group constituents. Most importantly, the ordered structure is induced by the surface reconstruction during epitaxy and is metastable in the bulk of the film. Glide through ordered planes disrupts the order pattern and reduces this metastability, and so is energetically favorable. This presents a unique situation where dislocations receive an additional driving force for glide. The additional glide force reduces the critical thickness of pseudomorphic material, but should also beneficially increase the glide length of metamorphic material. In addition, the distribution of dislocations is heavily skewed towards those that disrupt the order pattern. New dislocations can form upon order-disorder transitions in a metamorphic buffer as glide becomes more energetically favorable on different glide planes, necessitating redesign of the buffer structure. Further implications are discussed, as well as strategies to improve stability of pseudomorphic material and reduce the dislocation density of metamorphic material.