Growth of High Quality, MOCVD Grown Ga-Polar GaN Layers on GaN Substrates after Novel Reactive Ion Etching

In this paper we present morphological, structural, optical and chemical characteristics of GaN homoepitaxial layers grown by MOCVD on Ga-polar (0001) substrates prepared using a novel reactive ion etching (RIE) procedure. The layers show microscopically featureless morphology and exhibit the step-flow growth mode with step heights of c/2 as evidenced by DIC optical and atomic force microscopy, respectively. Cross-sectional TEM illustrated the absence of threading defects. Low temperature (4.2 K) photoluminescence from this defect-free layer shows donor- and acceptor-bound exciton peaks with linewidth below 1 meV. Secondary ion mass spectroscopy revealed an abrupt change of the concentration of all the typical contaminants (O, C, Si, H) across the epilayer/substrate interface. The results indicate that the RIE process based on Ar–SiCl4–SF6 chemistry is the right tool for preparing Ga-polar GaN substrates for the growth of high quality homoepitaxial layers.