Structural and optical properties of GaN films grown on GaAs substrates by molecular beam epitaxy

GaN films are grown on [0 0 1] GaAs substrates by plasma-assisted molecular beam epitaxy using a three-step process that consists of a substrate nitridation, deposition of a low-temperature buffer layer, and a high-temperature overgrowth. X-ray diffraction and transmission electron microscopy indicate that this method promotes prismatic growth of c-oriented α-GaN. Photoluminescence studies show that the emission from cubic β-GaN inclusions dominates the spectrum.