Growth of thick and pure cubic GaN on (0 0 1) GaAs by halide VPE

To obtain a thick and pure cubic GaN layer, a hybrid growth of the halide v apor phase epitaxy (HVPE) and the metal organic MBE (MOMBE) was performed. An about 20 nm thick GaN buffer layer was grown on (0 0 1) GaAs by MOMBE us ing tertiary butyl hydrazine in a MBE chamber. Thick GaN layers were grown on it by a conventional HVPE system using H-2 as a carrier gas. When the th ickness was less than 2 mu m, the hexagonal component in the grown layer wa s less than 1% for a V/III ratio of 200, but it increased exponentially wit h an increase of the growth time and it became about 10% at 5 mu m (2 h gro wth) and about 40% at 10 mu m (3 h growth). These thicknesses are about thr ee times larger than those generally obtained by GSMBE or MOVPE with the sa me hexagonal content. The grown surface became rough with an increase of th ickness and therefore of hexagonal content. Photoluminescence was very poor even for a pure cubic GaN probably due to autodoping by arsenic. (C) 1999 Elsevier Science B.V. All rights reserved.