The effect of intentional O introduction, at the surface of GaAs, upon its native surface states was studied. The O was caused to interact with the surface of GaAs by 3 different means. Firstly, by growing native oxides. Secondly, by exposure to O plasma in an electron cyclotron resonance plasma reactor and, thirdly, by high-energy O-ion irradiation. Thermally stimulated exo-electron emission spectroscopy was used to estimate the relative densities and energies of the surface states which were introduced by these 3 different methods. Of the 2 native defect levels, found by thermally stimulated exo-electron emission at 325K (0.7eV below Ec) and 415K (0.9 below Ec), the former was seen to broaden or split into multiple peaks for each of the methods. Multiple peaks in the thermally stimulated exo-electron emission indicated the presence of a closely-spaced band of defect levels. The results therefore showed that O-related complexes contributed to the formation of a band of defects which was centered at 325K, in the thermally stimulated exo-electron emission and was related to an energy level which was 0.7eV below Ec: the EL2 defect level. These results thus confirmed that the thermally stimulated exo-electron emission peak at 0.7eV below Ec was related to O-induced defects, whereas the peak at 0.9eV was unaffected by the presence of O-related species.

Detection of Oxygen-Related Defects in GaAs by Exo-Electron Emission Spectroscopy. S.S.Hulluvarad, M.Naddaf, S.V.Bhoraskar: Nuclear Instruments and Methods in Physics Research B, 2001, 183[3-4], 432-8