Overlayer metallicity and Fermi-level pinning at the Ca-GaAs(110) interface

Abstract

Photoemission spectroscopy is used to study chemistry and band bending at the Ca-GaAs(110) interface as a function of metal coverage. An intermediate position of the Fermi level (EF ) resulting from the formation of adsorbate-induced states and native defects is found at low coverage at 0.75–0.9 eV above the top of the valence-band maximum (VBM). An additional abrupt shift of EF leading to a final position 0.55 eV above VBM takes place when metallicity develops in the overlayer. The results for this interface supports Schottky-barrier models based on gap states induced or modified by the metal.