Fermi level pinning and chemical interactions at metal–InxGa1−xAs(100) interfaces

Abstract

Soft x-ray photoemission spectroscopy (SXPS) measurements of metals on clean, ordered InxGa1−xAs(100) surfaces reveal that Fermi level stabilization energies depend strongly on the particular metal, i.e., the Fermi level is not pinned. For InxGa1−xAs, x>0, the range of Fermi level movement is comparable to or greater than the semiconductor band gap. For the same metal on different alloys, we observe regular trends in stabilization energies. The trend for Au is strikingly different from previous, air-exposed values. Our results challenge Schottky barrier models based on simple native defects, metal-induced gap states, or the ‘‘common-anion’’ rule. Observed variations in semiconductor outdiffusion provide a chemically-modified interface work function model which accounts for the data across the alloy series.