The surface morphology of metalorganic chemical vapor deposited epilayers was studied by means of atomic force microscopy. The theoretical growth morphology was first derived from the crystal structure. Connected nets were found for the {00•2}, {1¯1•1} and {1¯1•0} faces. Experimental results showed that, on Ga-terminated films, both the (00•1) and {1¯1•0} faces were present over a considerable temperature range. The (00•1) surfaces exhibited growth spirals that emerged from screw dislocations. The single or double spirals were composed of monatomic steps. The double steps tended to split at the spiral centres. This was attributed to entropic repulsion and a high surface diffusion. Most spiral centres were accompanied by hollow cores whose size was greater than predicted. The large diameter of the hollow cores was tentatively explained in terms of the precipitation of vacancies along the dislocations.

An Atomic Force Microscopic Study of a Temperature-Dependent Morphology Transition in GaN Grown on Sapphire. F.K.De Theije, A.R.A.Zauner, P.R.Hageman, W.J.P.Van Enckevort, P.K.Larsen: Journal of Crystal Growth, 1999, 197[3], 37-47