Scanning electron microscope studies of GaN films grown by hydride vapor phase epitaxy

Scanning electron microscope studies of hydride vapor phase epitaxy (HVPE) grown GaN films are reported. Two films grown on sapphire and having thickn esses of 3 and 20 mu m and a GaN film deposited on SIC without any buffer l ayer were studied. In the thicker GaN/sapphire films some crescent-shaped g rowths and small growth pyramids were observed and were shown to have a hig her electron concentration than the matrix, The surface morphology of the t hin GaN/sapphire film was featureless. Microcathodoluminescence (MCL) and e lectron beam induced (EBIC) measurements also revealed the presence of a mo saic nonuniformity of the density of recombination centers in both samples. The diffusion length of holes in these HVPE grown films was shown to be 2- 3 mu m. For the GaN/SiC a network of dark lines possibly related to the dis locations formed at the GaN/SiC interface was detected in the EBIC mode. (C ) 1999 Elsevier Science Ltd. All rights reserved.