Transmission electron microscopic studies of GaN grown on silicon carbide and sapphire by laser induced molecular beam epitaxy

Transmission electron microscopy (TEM) studies have been performed on GaN e pitaxial films grown on SiC and sapphire substrates by laser induced molecu lar beam epitaxy (LIMBE). Similar types of threading dislocations are forme d in the GaN epilayers but with different dislocation densities. They have edge, mixed and screw type of Burgers vectors, predominantly the first type . In addition to threading dislocations, inversion domain boundaries are fo und in the GaN epilayer grown on sapphite. The results suggest that the inv ersion domain boundaries have Ga-N bonds between domains and the adjacent m atrix without displacements along the c-axis in the basal planes. (C) 1999 Elsevier Science S.A. All rights reserved.