High quality NiGe/Ge diodes for Schottky barrier MOSFETs

Husain, M. K., Li, X. and de Groot, C.H. (2008) High quality NiGe/Ge diodes for Schottky barrier MOSFETs. E-MRS Spring Meeting,, Strasbourg, France. (In Press)

Abstract

Schottky barrier (SB) Ge channel MOSFETs suffer from high drain/body leakage at the required elevated substrate doping concentrations. Here we show that electrodeposited Ni-Ge and NiGe/Ge Schottky diodes on highly doped Ge show very low off current, which might make them suitable for SB-MOSFETs. Diodes were fabricated by electrodeposition of Ni on n-type Ge having a resistivity of 0.005-0.02 ohm-cm. Germanidation was performed by annealing the samples in an inert atmosphere at temperatures up to 500° C. X-ray diffraction analysis and the scanning electron microscope images confirm the existence of only polycrystalline NiGe phase at the various annealing temperatures. The current density vs. voltage curves of both of the as deposited Ni/n-Ge and the annealed NiGe/n-Ge diodes show the forward current density being ~5 orders in magnitude higher than the reverse current density at 1 volt bias. Moreover, at low forward biases, there is a sharp overlap of the forward current density for the as deposited Ni/n-Ge and NiGe/n-Ge Schottky diodes. This SB height remains virtually constant at 0.52 eV under annealing indicating consistent Fermi pinning in the Ge band gap. The series resistance decreases with annealing in agreement with four point probe measurements indicating the lower specific resistance of NiGe as compared to Ni, which is crucial for high drive current in SB-MOSFETs. The experimental data of the diodes are used to calibrate numerical simulations of the SB-MOSFETs.

This record has no associated files available for download.

Contributors

Author: C.H. de Groot

Download statistics