SURFACE FLATTENING OF GAN BY SELECTIVE-AREA METALORGANIC VAPOR-PHASE EPITAXY

The surface flattening of GaN films by selective area metalorganic vap or phase epitaxy is demonstrated. Selectively grown GaN films 30-50 mu m in diameter have smooth surfaces with neither bunched steps nor rid ge growth. These surfaces consist of bilayer height spiral steps that originate from screw dislocations. The surface flattening is probably due to the disappearance of steps at the edges of the selectively grow n GaN. Desorption of the film forming precursors from the growing surf ace is increased on the smooth GaN surface during growth at substrate temperatures of 1000 degrees C ol higher in H-2 carrier gas. A low dis location density is essential for a smooth GaN surface, because the sp irals determine the step structure.