The initial growth of hexagonal GaN films grown on Si(1 1 1) substrates coated with an ultra-thin SiC buffer layer was studied. It was found that a 2.5-nm-thick SiC layer is an effective buffer layer for GaN growth on an Si(1 1 1) 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 submicron-sized grains. Under N-rich growth conditions, the initial GaN nucleations saturated at a diameter of about 50 nm (measured at the film surface). The grown GaN films showed statistical roughening of the surface and a characteristic columnar structure. The yellow-band luminescence (YL) was sensitive to the microstructures of the GaN films prepared under almost the same growth conditions, suggesting that the Ga-vacancy is not the sole source of YL. (C) 2002 Elsevier Science B.V. All rights reserved.