Gallium-gallium weak bond that incorporates nitrogen at atomic steps during GaN epitaxial growth

Abstract

Growth of high-quality epitaxial thin films of GaN is indispensable for the energy-saving power electronics and the clarification of the mechanism of the epitaxial growth, which is unachieved yet, is essential to advance nanoscience and technology. We here report quantum-theory-based first-principles calculations that elucidate atomic structures and formation energies of the surface steps of GaN (0001) surfaces, unveil atom-scale elementary processes of N incorporation at the step edges, and then provide a microscopic picture of the step-flow epitaxial growth of GaN for the first time. We find that the NH unit produced after the decomposition of NH3 on the surface terrace diffuses to the stable step edges and is incorporated in the GaN thin film, thus clarifying an elementary process of the step-flow epitaxial growth. Our calculations indicate that the essential factor to promote the epitaxial growth is the presence of the Ga-Ga weak bond on the growing surface.