Effects of surface chemical treatment on the formation of metal GaAs interfaces

We have used synchrotron radiation photoemission spectroscopy to investigat e the chemical interactions at metal/GaAs interfaces during deposition of A u and In onto GaAs(100) surfaces that are chemically treated in etching sol utions. We determine that there exists a thin native oxide layer on the sur face that is treated in H2SO4 solution. Au reacts with the oxide overlayer to generate AuGa alloy, but In does not interact appreciably with the oxide overlayer leading to;the island growth of the In overlayer at high In cove rages. We confirmed (NH4)(2)S-x treatment leads to a GaAs surface that is t erminated with sulfur. For the Au deposition onto this surface, alloy forma tion and segregates both at interfacial regions and on metallic overlayers are significantly suppressed, leading to the island growth of the Au overla yer. On the other hand, at initial stages of In deposition, In strongly int eracted with the (NH4)(2)S-x-treated surface to generate a thin layer of In xGa1-xAs alloy on which the In overlayer formed in a layer-by-layer fashion . We also investigate the effects of surface treatments in the Fermi level pinning. (C) 1999 American Vacuum Society. [S0734-2101(99)01302-0].