Effects of reactive ion beam treatment of a sapphire surface to optimite the deposition of GaN films

We examined the possibility of employing the surface treatment of sapphire using reactive ion beam (RIB) pretreatment as an alternative process for Ga N growth in metalorganic chemical vapor deposition (MOCVD). As a result of the RIB treatment, etching of the sapphire surface and the formation of a v ery thin, disordered AlON layer was observed which was partially crystalliz ed during the main growth of GaN. Reduction in both dislocation density and lattice strain of GaN on RIB treated sapphire was obtained. Partial crysta llization in the RIB layer promoted two-dimensional growth on the crystalli zed regions and relieved the misfit strain through relaxation of the disord ered RIB layer. The optical properties of the GaN films could be optimized by the proper choice of the ion beam energy. The present results clearly sh ow that RIB pretreatment of the sapphire surface can be used to improve the properties of GaN films grown by MOCVD. (C) 2000 American Institute of Phy sics. [S0021-8979(00)06011-4].