X-ray photoelectron spectroscopy characterization of AlGaN surfaces exposed to air and treated in NH4OH solution

Chemical properties of Al0.17Ga0.83N surfaces exposed to air and treated in an NH4OH solution were systematically investigated by x-ray photoelectron spectroscopy (XPS). An air-exposed sample showed highly nonstoichiometric s urface which included a large amount of Ga and Al oxides. The angle-resolve d XPS analysis revealed that the natural oxide layer possessed a complicate d composition distribution in depth and that the Al-oxide component was dom inant on the topmost layer. A drastic reduction of such Al-oxide component as well as Ga-related oxide was achieved after the treatment in an NH4OH so lution at 50 degrees C for 10 min, resulting in a constant in-depth composi tion distribution. The NH4OH-based treatment was found to enhance the inten sity of the E2 (high) Raman peak and to reduce the root-mean-square value o f surface roughness. (C) 2000 American Institute of Physics. [S0003-6951(00 )04920-2].