Nature of native oxide on GaN surface and its reaction with Al

In this letter, we describe the surface properties of GaN thin films grown on sapphire substrate by molecular beam epitaxy, as revealed by ultraviolet and x-ray photoelectron spectroscopic and Auger electron spectroscopic studies. The samples are seen to contain overlayer of native oxides, which are predominantly in the Ga2O3 form. Ammonia is shown to be a good etchant for these native oxides. Furthermore, we investigated the early stages of the reaction of monolayer Al with a GaN surface covered with native oxide, Aluminum reacts preferentially with the surface oxygen and leads to the formation of a mixture of oxides at the interface. (C) 1996 American institute of Physics.