ULTRAVIOLET-LIGHT-INDUCED OXIDE FORMATION ON GAAS-SURFACES

We present a study of deep-ultraviolet-light-enhanced (4.1 < hν< 5.1 eV) oxygen reactions on GaAs from submonolayer to several monolayers coverage. The reaction is nonthermal and does not involve gas-phase excitation or dissociation of O2. Our experiments show a distinct wavelength and coverage dependence for the photoenhancement. X-ray photoelectron spectroscopy has been used to examine the chemical nature of the oxygen adsorbate and the GaAs oxides in order to find intermediate reaction species and evidence of the reaction pathways. The roles of photons and photogenerated carriers in the reaction enhancement mechanism are discussed. The results indicate that a mechanism based on photoemission of electrons into the growing oxide film is most in accord with the experimental observations. Such electron emission would increase the field-driven transport of oxygen to the GaAs interface. © 1990 American Institute of Physics.