Molecular-beam homo-epitaxial films, on both of the c-plane surfaces of bulk crystals, were studied by means of reflection high-energy electron diffraction. The substrate surfaces were prepared by mechanical polishing [GaN(00•1)A] or by mechanochemical polishing [GaN(00•¯1)B]. On the B surface, Ga-rich reconstructions were observed. On the A surface, a (2 x 2) reconstruction was observed. Both reconstructions were much sharper than those seen on GaN films which were grown on sapphire. Preliminary investigation of the A surfaces revealed decorated step edges.

Structure and Composition of GaN(0001) A and B Surfaces. R.Held, G.Nowak, B.E.Ishaug, S.M.Seutter, A.Parkhomovsky, A.M.Dabiran, P.I.Cohen, I.Grzegory, S.Porowski: Journal of Applied Physics, 1999, 85[11], 7697-704