THE INFLUENCE OF OXYGEN-ADSORPTION ON THE ELECTRONIC SURFACE-STATES AND THE FERMI LEVEL PINNING ON THE CLEAN, POLAR GAAS(111) SURFACE

A more detailed analysis of our recently published results on the electronic properties of the clean, polar GaAs(111) surface exposed to oxygen obtained by photoemission yield spectroscopy (PYS) and surface photovoltage spectroscopy (SPS) associated with Auger electron spectroscopy (AES) control, is presented. It has been noted that with increasing oxygen exposure the absolute band bending eV(s) also increases, which causes a shift of the Fermi level E(F) from the upper part to the middle part of the band gap, and for the final oxygen exposure of 10(7) L pinning al about 0.95 eV above the top of the valence band at the surface E(vs). Moreover, an increase of the absolute band bending eV(s) with increasing oxygen exposure corresponded to an increasing amplitude of the surface photovoltage for h-nu > E(g) as well as to a shift of the low energy threshold of the surface photovoltage for hv < E(g).