The influences of chemical treatment and thermal annealing of AlxGa1-xN (x = 0.20) have been investigated by X-ray photoelectron spectroscopy (XPS). XPS analysis showed that successive chemical treatments and annealing produced changes in the stoichiometry of the AlxGa1-xN surface, with the surface concentration of N increasing and Al and Ga decreasing with increasing temperature. Band bending occurred at the AI(x)Ga(1-x)N surface, in parallel with the observed changes in stoichiometry. These results are discussed in the context of the creation of surface states via the activation of vacancies and induced by defects. These findings point towards the possibility of selecting and/or engineering the band structure at AlxGa1-xN surfaces through a combination of surface preparation and annealing. (c) 2005 Elsevier B.V. All rights reserved.