Surface reconstructions and adatom kinetics of Si on the (00•1) and (00•¯1) GaN surfaces were studied by means of scanning tunnelling microscopy, electron diffraction and first-principles calculations. For Si coverages of near to half of a monolayer, a 2 x 2 structure was observed and was interpreted in terms of a model which consisted of a Ga adatom on a monolayer of 3Ga + 1Si, and a SiGa atom in the third layer. At higher Si coverages, disordered 2 x 2 domains and 1 x 1 domains were found to coexist. After annealing above 300C, the 1 x 1 regions became dominant and a 4 x 4 structure was seen near to step edges. It was concluded that the Si adatoms tended to reside in sub-surface sites on the Ga-polar surface. The surface morphology in the presence of Si was smooth for the (00•1) surface, but rough for the (00•¯1) surface. This difference was attributed to the presence of multiple Ga surface layers, in the former case, which enhanced surface diffusivities.

Silicon on GaN(0001) and (000¯1) Surfaces. C.D.Lee, R.M.Feenstra, A.L.Rosa, J.Neugebauer, J.E.Northrup: Journal of Vacuum Science and Technology B, 2001, 19[4], 1619-25