Homo-epitaxial GaN growth on exact and misoriented single crystals: suppression of hillock formation

GaN single crystals were used as substrates for MOCVD growth. The (0 0 0 (1) over bar) plane of the substrate crystals was polished to obtain off-angle orientations of 0, 2, and 4 degrees towards the [1 0 (1) over bar 0] direction. The highest misorientation resulted in a reduction of the hexagonal hillock density by nearly two orders of magnitude as compared with homo-epitaxial films grown on the exact (0 0 0 (1) over bar) surface. The features that are still found on the 4 degrees off-angle sample after growth can be explained by a model involving the interaction of steps, introduced by the misorientation, and the hexagonal hillocks during the growth process. Following from this explanation it could be concluded that surface diffusion is found to be not important during growth on the N-side. The material quality of the N-side was examined by photoluminescence (PL) measurements. The PL spectrum measured at 5 K shows dominant donor bound excitons with a FWHM of 1.4 meV as well as free excitonic transitions. (C) 2000 Elsevier Science B.V. All rights reserved.