Mechanism of misfit stress relaxation during epitaxial growth of GaN on porous SiC substrates

Abstract

A decrease in the density of threading dislocations has been observed during the epitaxial growth of GaN layers on porous silicon carbide (PSC) substrates by means of chloride hydride vapor phase epitaxy. It is established that, in the early growth stage, the substrate is capable of redistributing stresses in the growing heterostructure, which leads to relaxation of the lattice misfit stresses via generation of a superlattice of planar defects. In the subsequent growth stage, these defects prevent the propagation of threading dislocations. Owing to this phenomenon, 1-μm-thick GaN layers on PSC can be obtained with a density of dislocations reduced by two orders of magnitude as compared to epilayers of the same thickness grown on nonporous substrates.