Effects of the surface stoichiometry of seeds on GaN layer growth by hydride vapour phase epitaxy

The effect of the atmosphere in a reactor prior to hydride vapour phase epitaxy on the surface stoichiometry of both the GaN template and layer growth was studied. The surface stoichiometry of metallic Ga layers was clarified by X-ray photoelectron spectroscopy using templates without NH3 protection. The metallic Ga layer acted as a mask and exerted a significant effect on the subsequent epitaxial layer growth mode. GaN grown on the template without protection followed island growth in the initial growth stage. In contrast, GaN epitaxy on the template with NH3 protection quickly converts to pseudo-2D growth. The images of CL illustrate that the GaN epilayer on the template without protection has a lower dislocation density than the GaN epilayer grown on the template with NH3 protection. Reasons behind this effect have been discussed.