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 epitaxial films grown on SiC and sapphire substrates by laser induced molecular beam epitaxy (LIMBE). Similar types of threading dislocations are formed 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 found in the GaN epilayer grown on sapphire. The results suggest that the inversion domain boundaries have Ga–N bonds between domains and the adjacent matrix without displacements along the c-axis in the basal planes.