The Influence of Buffer Layer Growth Parameters on the Microstructure and Surface Morphology of GaN on Sapphire Substrates Correlated with in-situ Reflectivity

GaN low temperature nucleation and high temperature buffer layers have been grown by metalorganic vapour phase epitaxy. The effect of nucleation layer annealing temperature and buffer layer growth temperature on their microstructure and morphology has been examined by atomic force microscopy and X-ray diffraction and correlated to the in-situ reflectivity obtained from the growing layers. For the nucleation layer, the anneal was observed to lead to the formation of GaN nucleates on the substrate surface, the properties of which changed markedly with temperature. Surface pits resulting from dislocations with a screw component have been observed and the variation of the density with growth temperature ascertained.