Growth evolution of cubic-GaN on sapphire (0001) substrate by metalorganic molecular beam epitaxy

Cubic GaN (c-GaN) could be grown on sapphire (0001) substrates by metalorganic molecular beam epitaxy (MOMBE) under a Ga-rich condition at a relatively high growth temperature (800 degrees C). The growth was carried out with two different substrate treatments, either nitridation or deposition of a GaN buffer layer at a low temperature (400 degrees C). In both case, the grown layer contains not only c-GaN but also hexagonal GaN (h-GaN). The ratio of h-GaN to c-GaN is greatly reduced by using the buffer layer. Based on the experimental results, a growth model of c-GaN is proposed. (C) 1999 Elsevier Science B.V. All rights reserved.