The initial growth of hexagonal GaN films grown on 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. Consequently, the GaN films had a flat surface and an almost stacking-fault-free microstructure. The initial GaN nucleations quickly coalesced laterally to sub-micron sized grains. Under N-rich growth conditions, the initial GaN nucleations saturated at a diameter of about 50nm (measured at the film surface). The grown GaN films showed statistical roughening of the surface and a characteristic columnar structure. The yellow-band luminescence was sensitive to the microstructures of the GaN films prepared under almost the same growth conditions, suggesting that the Ga-vacancy was not the sole source of 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