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Elsevier, Microelectronic Engineering, 7-9(86), p. 1599-1602

DOI: 10.1016/j.mee.2009.03.097

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Inhomogeneous Ni/Ge Schottky barriers due to variation in Fermi-level pinning

This paper is available in a repository.
This paper is available in a repository.

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Abstract

To achieve high performance Ge nMOSFETs it is necessary to reduce the metal/semiconductor Schottky barrier heights at the source and drain. Ni/Ge and NiGe/Ge Schottky barriers are fabricated by electrodeposition using n-type Ge substrates. Current (I)–voltage (V) and capacitance (C)–voltage (V) and low temperature I–V measurements are presented. A high-quality Schottky barrier with extremely low reverse leakage current is revealed. The results are shown to fit an inhomogeneous barrier model for thermionic emission over a Schottky barrier. A mean value of 0.57 eV and a standard deviation of 52 meV is obtained for the Schottky barrier height at room temperature. A likely explanation for the distribution of the Schottky barrier height is the spatial variation of the metal induced gap states at the Ge surface due to a variation in interfacial oxide thickness, which de-pins the Fermi level.