Effect of nitridation on crystallinity of GaN grown on GaAs by MBE

GaN films are grown on [001] 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. Films are evaluated by X-ray diffraction and the dependence of crystalline quality on the nitridation temperature is studied. It is demonstrated that nitridation has to be performed at low-temperature to achieve c-oriented alpha-GaN. Higher nitridation temperature promotes formation of mis-oriented domains and beta-GaN inclusions (c) 2006 Elsevier B.V. All rights reserved.