Insight into the step flow growth of gallium nitride based on density functional theory

Abstract

We report the first-principles calculations based on the density-functional theory that elucidate the mechanism of the epitaxial growth on the mixed GaN (0001) surface which consists of the Ga-adatom and the Ga-H structural motifs. We find that the source-gas molecule NH3 is decomposed on the Ga-adatom site to an NH unit and the resulting NH unit diffuses in a newly found concerted way in which the Ga adatom assists in the NH diffusion by annihilating dangling bonds nearby. We also identify the structures of the H-covered step edges and obtain their formation energies. We find plausible reaction pathways near the step edges in which the NH units and Ga adatoms are incorporated in the epitaxial films, forming new units of GaN. The obtained final structures are certainly the manifestation of the step-flow mechanism of the epitaxial growth of GaN.