Surface characterization of GaN and AlGaN layers grown by MOVPE

Surface properties of GaN and Al0.17Ga0.83N materials grown by metal organi c vapor phase epitaxy (MOVPE) were systematically investigated by X-ray pho toelectron spectroscopy (XPS). Air-exposed samples showed highly non-stoich iometric surfaces, which included a large amount of natural oxides. Deposit ion of Al on the air-exposed GaN surface caused interfacial reactions, resu lting in the formation of oxide lavers including: Al2O3 and Ga oxide at the interface. A natural oxide layer of AlGaN surface possessed a complicated composition distribution in depth where the Al-oxide component was dominant on the topmost layer. Such natural oxide layers were found to be removed f rom GaN and AlGaN surfaces after the treatment in an NH4OH solution at 50 d egreesC for 10 min, resulting in oxide-free and well-ordered surfaces. (C) 2001 Elsevier Science B.V. All rights reserved.