Thick GaN Films Grown on Sapphire: Defects in Highly Mismatched Systems

摘要

In this paper, we review the present knowledge of the defects in thick GaN films grown by hydride vapor phase epitaxy (HVPE) on sapphire substrates. We summarize the defects present in such highly mismatched system into three main categories: large-scale nonuniformities; microstructure crystallographic defects; and point defects. We begin by describing the layer structure typical for thick films grown at very high growth rates, and concentrate on large-scale three-dimensional defects and their impact on the crystal quality. Then we briefly review the current understanding of the variety of extended structural defects with the emphasis on their role in the morphology and relaxation mechanisms in thick heteroepitaxial layers. The discussion is completed by reviewing the point defects in HVPE nitride materials and their influence on the optical properties of GaN films.