Low-Temperature Growth of GaN Epitaxial Layers with Buffer Layers by Reactive Close-Spaced Method

Abstract

GaN epitaxial layers with buffer layers were grown on (0001) sapphire substrates by direct reaction of Ga and NH3 at the low temperature of 750°C. The buffer layers were deposited on the substrates by using GaN-coated graphite boats at temperatures below 750°C in Ar flow before the epitaxial layers were grown, where GaN films coated on the graphite boats acted as a source material in the deposition of the buffer layers. The Hall mobility of the GaN epitaxial layers grown with the buffer layers was approximately 50 cm2/(V·s), whereas that of the GaN epitaxial layers grown without the buffer layers was approximately 2 cm2/(V·s). The crystallinity of the GaN epitaxial layer was improved by being grown on the buffer layer. The buffer layer deposited by using the GaN-coated graphite boat played a role similar to that of the buffer layer deposited at low temperature by conventional metal-organic chemical vapor deposition.