A novel growth method was described for obtaining high-quality GaN films on sapphire substrates by means of low-pressure metal-organic vapour phase epitaxy. The object was to obtain epitaxy by lateral overgrowth; starting with self-organized islands on a GaN layer. It was recalled that classical epitaxy by lateral overgrowth was carried out via the coalescence of crystalline material which was grown selectively through striped windows in a dielectric mask. The classical process involved deposition and etching of the SiO2 or SiNx mask. The use of self-organised islands permitted the avoidance of these 2 steps. Such islands were obtained after a growth mode change which was caused by Si impurities. They had {1¯1•1} lateral facets and an upper {00•1} facet. Their densities and sizes depended upon the Si treatment and growth temperature, and could be controlled by these 2 factors. The overgrowth of optimised islands led to a marked improvement in the material quality. Defect analysis revealed only the presence of threading dislocations, with a density of 5 x 108 and 9 x 108/cm2; as compared with 1010/cm2 for conventionally produced layers.

Growth of High-Quality GaN by Low-Pressure Metal-Organic Vapour Phase Epitaxy from 3D Islands and Lateral Overgrowth. H.Lahrèche, P.Vennéguès, B.Beaumont, P.Gibart: Journal of Crystal Growth, 1999, 205[3], 245-52