Current–voltage characteristics of Schottky barriers with barrier heights larger than the semiconductor band gap: The case of NiGe∕n-(001)Ge contact

Current–voltage-temperature characterization has been performed on NiGe∕n-(100)Ge Schottky contacts that were formed by the solid-state reaction of Ni with Ge. An effective barrier height of 0.732–0.735eV, which is larger than the band-gap 0.66eV of Ge, was obtained. A physical model describing the current transport mechanism in a Schottky contact with a barrier height larger than the semiconductor band gap is proposed and discussed on the basis of thermionic-field emission as the dominant transport mechanism. The observation of a barrier height larger than the semiconductor band gap should be of technological importance as it suggests that NiGe is an ideal contact and Schottky source/drain material in Ge-based p-metal-oxide-semiconductor field-effect-transistors.