Absence of Fermi level pinning at metal-In_xGa_1-xAs(100) interfaces

Soft x-ray photoemission spectroscopy measurements of clean, ordered InxGa1-xAs (100) surfaces with Au, In, Ge, or Al overlayers reveal an unpinned Fermi level across the entire In alloy series. The Fermi level stabilization energies depend strongly on the particular metal and differ dramatically from those of air-exposed interfaces. This wide range of Schottky barrier height for III-V compounds is best accounted for by a chemically induced modification in metal-alloy composition.