Morphology of facets on vapor-grown AIN crystals

Single crystals of AlN were grown using the sublimation–recondensation method. On the Al-terminated surface, (0 0 1) and (1 1 3) facets were observed. On the basal plane facets, step flow growth was revealed by atomic force microscopy measured after the growth. The steps were one molecular layer high and were arranged in spirals near the outlets of screw dislocations, but consisted of straight segments along the 〈1̄ 1 0〉 directions on the most of the surface. We discuss the shape of the steps as the result of competing processes: re-evaporation of deposited species and their diffusion along the steps. An estimation of the activation energy for diffusion of Al atoms along th steps gave approximately 0.5 eV.