Interfacial chemistry and Schottky-barrier formation of the Ni/InP(110) and Ni/GaAs(110) interfaces

The room-temperature interaction of Ni overlayers with cleaved GaAs(110) and InP(110) is investigated with valence-band and core-level soft x-ray photoemission spectroscopies. It is shown that Ni reacts strongly with both substrates leading to the formation of Ni phosphides or arsenides and segregation of metallic components. At room temperature a reacted-phase interlayer of several A{} is formed, followed by lateral layers of nonreacted Ni. In the case of the Ni/GaAs interface the reaction is less pronounced. Some other spectroscopic features of the metal overlayers are also discussed. The pinning for both n-type and p-type GaAs is for monolayer coverages established to be 0.7±{}0.1 eV below the top of the conduction band, which is agreement with electrical measurements on thick diodes. For the Ni/p-type InP interfaces the pinning position of 0.9 eV above the valence-band maximum is shown to be established for a coverage as low as 0.1 A{} of Ni.