Direct Observation of Adsorbate-Induced Band-Gap States on GaAs(110)

Normally unoccupied adsorbate-induced states within the GaAs band gap were studied by measurement of ultraviolet-photoemission spectra from pulsed-laser-excited surfaces. Strikingly similar discrete structures within the gap were observed for submonolayer coverages of both chemisorbed oxygen and gold. The implications of these results for the understanding of Fermi-level pinning at interfaces are discussed. © 1986 The American Physical Society.