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

Current-voltage-temperature characterization has been performed on NiGen- (100) Ge Schottky contacts that were formed by the solid-state reaction of Ni with Ge. An effective barrier height of 0.732-0.735 eV, which is larger than the band-gap 0.66 eV 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.