A novel growth method was proposed for obtaining  high quality films on sapphire by using low-pressure metal-organic vapour phase epitaxy. The aim was to achieve epitaxy via lateral overgrowth; starting with self-organized islands on a GaN layer. Classical lateral overgrowth was performed by the coalescence of material which was grown selectively through striped windows. This usually involved the deposition and etching of a mask. The use of self-organized islands obviated those steps. The islands were produced by a growth-mode change which was induced by Si impurity. They had {1¯1•1) lateral facets and a top {00•1} facet. Their densities and sizes depended upon the added Si and the growth temperature. The overgrowth of optimum islands led to a sharp improvement in the material quality. Defect analysis revealed the presence of threading dislocations alone, at a density of 5 x 108 to 9 x 108/cm2. The usual technique yielded densities of the order of 1010/cm2.

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