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 thicknesses of 3 and 20 μm and a GaN film deposited on SiC without any buffer layer were studied. In the thicker GaN/sapphire films some crescent-shaped growths and small growth pyramids were observed and were shown to have a higher electron concentration than the matrix. The surface morphology of the thin GaN/sapphire film was featureless. Microcathodoluminescence (MCL) and electron beam induced (EBIC) measurements also revealed the presence of a mosaic 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 μm. For the GaN/SiC a network of dark lines possibly related to the dislocations formed at the GaN/SiC interface was detected in the EBIC mode.