The influence of annealing temperature on the optical properties of surface electron accumulation layers in n-type (100) InAs wafers has been investigated by Raman spectroscopy. It exhibits that Raman peaks due to scattering by unscreened LO phonons disappear with increasing temperature, which indicates that the electron accumulation layer in InAs surface is eliminated by annealing. The involved mechanism was analyzed by X-ray photoelectron spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy. The results show that amorphous In2O3 and As2O3 phases are formed at InAs surface during annealing and, meanwhile, a thin crystalline As layer at the interface between the oxidized layer and the wafer is also generated which leads to a decrease in thickness of the surface electron accumulation layer since As adatoms introduce acceptor type surface states. (C) 2013 Elsevier B.V. All rights reserved.