Surface oxidation and growth-derived oxygen contamination for Al0.05Ga0.95Sb films, grown by metalorganic chemical vapour deposition (MOCVD), were systematically investigated using an X-ray photoelectron spectroscopy (XPS) system with high energy resolution. The Sb 3d(5/2) and O 1s peaks were well resolved, as were the Ga 3d peaks. All samples investigated show oxide layers (Al2O3, Sb2O3 and Ga2O5) on their surfaces. In particular, the percentage of aluminium oxide was very high at the sample surface compared to AlSb. Carbon incorporation was also examined. Adventitious surface carbon was high; however, in the bulk material carbon was below the detection limit of XPS and secondary ion mass spectroscopy (SIMS). These results indicate extremely low carbon content for the MOCVD growth of Al0.05Ga0.95Sb epilayers. (C) 2004 Elsevier B.V. All rights reserved.