Surface morphology of cubic and wurtzite GaN films

We describe a comparative study of surfaces of gallium nitride films grown by a variety of techniques at low growth temperatures molecular beam epitaxy and laser-assisted chemical vapour deposition.as well as by metalorganic chemical vapour deposition. The cubic, wurtzite and mixed phase cubic–wurtzite films were grown on buffers, these included ultrathin 4 nm.SiC as well as more commonly used AlN. We find that the surface morphology of GaN films grown by MBE shows micrometer-scale structures which reflect the symmetry of the film. Surface topography may thus be used as an identification measure of film symmetry. Monochromatic cathodoluminescence images taken at the maximum of the band edge emission show granular structures reflecting surface morphologies, whereas similar structures are only very weakly visible in the redryellow band. q2000 Elsevier Science B.V. All rights reserved.