The initial growth of hexagonal GaN films, grown onto Si(111) substrates coated with an ultra-thin SiC buffer layer, was studied. It was found that a 2.5nm-thick SiC layer was an

effective buffer layer for GaN growth on an Si(111) substrate. Under Ga-rich growth conditions, Ga adatoms (in comparison to those under N-rich growth conditions) were highly mobile. The GaN films consequently had a flat surface and an almost stacking-fault free microstructure. The initial GaN nucleation quickly coalesced laterally to give sub-micron sized grains. Under N-rich growth conditions, the initial GaN nucleation saturated at a diameter of about 50nm (as measured at the film surface). The as-grown GaN films exhibited a statistical roughening of the surface and a characteristic columnar structure. The yellow-band luminescence was sensitive to the microstructures of GaN films prepared under almost the same growth conditions; thus suggesting that the Ga vacancy was not the only source of the yellow-band luminescence.

Initial Growth of Hexagonal GaN Grown on an Si(111) Substrate Coated with an Ultra-Thin SiC Buffer Layer. D.Wang, S.Yoshida, M.Ichikawa: Journal of Crystal Growth, 2002, 236[1-3], 311-7