Nickel and copper on cleaved indium phosphide: structure, metallurgy and electronic properties

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Abstract
Previous studies of Schottky barrier formation between metals and clean cleaved (110) surfaces of n-type InP have shown that chemically reactive metals (Ni, Fe, Al) pin the Fermi level relatively close to the conduction band whereas unreactive metals (Cu, Ag, Au) lead to pinning closer to mid-gap. The authors have selected Ni and Cu, as representative of each group, and studied the detailed interactions between these and the InP surface using a range of experimental techniques. These include LEED, Auger and photoemission using a laboratory source (He I radiation) as well as a synchrotron source. Nickel was found to interact very strongly with the surface resulting in the formation of nickel phosphides at the interface and the metallic indium diffusing out into the Ni contact. Copper interacts much more weakly with the surface, the core level and valence band photoemission spectra contrast markedly to the behaviour observed for Ni. The formation of Schottky barriers has also been probed by monitoring appropriate shifts in the photoemission spectra. The importance of the interactions at the interface on Schottky barrier formation is considered. Interface widths are also discussed.

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