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 epita xy and laser-assisted chemical vapour deposition) as well as by metalorgani c chemical vapour deposition. The cubic, wurtzite and mixed phase cubic-wur tzite films were grown on buffers, these included ultrathin (4 nm) SiC as w ell as more commonly used AlN. We find that the surface morphology of GaN f ilms grown by MBE shows micrometer-scale structures which reflect the symme try of the film. Surface topography may thus be used as an identification m easure of film symmetry. Monochromatic cathodoluminescence images taken at the maximum of the band edge emission show granular structures reflecting s urface morphologies, whereas similar structures are only very weakly visibl e in the red/yellow band. (C) 2000 Elsevier Science B.V. All rights reserve d.