INTERFACE CHEMISTRY AND SURFACE-MORPHOLOGY IN THE INITIAL-STAGES OF GROWTH OF GAN AND ALN ON ALPHA-SIC AND SAPPHIRE

The morphology and interface chemistry occurring during the initial stages of growth of GaN and AlN layers on alpha(6H)-SiC and sapphire have been examined. Films were grown using gas source molecular beam epitaxy (MBE) equipment containing an electron cyclotron resonance (ECR) plasma source to activate molecular nitrogen. The experiments consisted of sequential depositions of approximately one monolayer followed by X-ray photoelectron spectroscopy (XPS) analysis. Evidence for silicon nitride formation on the SiC surface was obtained from the studies of both the Si oxidation states and the substrate peak intensity dependence on film thickness. The growth of GaN on sapphire appeared to occur via Stranski-Krastanov mode, while the growth on SiC showed characteristics of three-dimensional growth. AlN grew in a layer-by-layer mode on both substrates.