A new method was developed in order to reduce markedly the dislocation density in a GaN film which was grown on a sapphire substrate. In this method, a very thin SiN layer was deposited onto the sapphire at a low temperature before growing a conventional low-temperature GaN buffer layer. Transmission electron microscopy showed that the density of threading dislocations, which originated from the interface between sapphire and GaN, decreased until it became undetectable. Levels of the order of 7 x 108/cm2 were found after using the conventional method. Atomic force microscopic studies of a deposited thin SiN layer indicated that nm-sized holes existed in the thin layer and probably enhanced lateral growth and decreased the dislocation density.

A New Method of Reducing Dislocation Density in GaN Layer Grown on Sapphire Substrate by MOVPE. S.Sakai, T.Wang, Y.Morishima, Y.Naoi: Journal of Crystal Growth, 2000, 221, 334-7