Surface flattening of GaN by selective area metalorganic vapor phase epitaxy

The surface flattening of GaN films by selective area metalorganic vapor phase epitaxy is demonstrated. Selectively grown GaN films 30-50 mu m in diameter have smooth surfaces with neither bunched steps nor ridge 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 grown GaN. Desorption of the film forming precursors from the growing surface 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 dislocation density is essential for a smooth GaN surface, because the spirals determine the step structure.