Morphological evaluation of epitaxial GaN grown on r-plane sapphire by metalorganic vapor-phase epitaxy

Morphological evaluation of epitaxial GaN films grown on r-plane sapphire substrates by atmospheric metalorganic vapor-phase epitaxy was investigated. The surface frequently showed rough morphology when the GaN was grown at conventional epitaxial conditions. It was found, however, that the surface roughness was improved by using appropriate combinations of growth temperature and low-temperature GaN buffer thickness. Thereby, a peak-to-valley value of the roughness was reduced from 4 μm to 0.8 μm. The rotation of crystallographic orientations was observed in the flattened GaN films.