Formation of nickel germanide on SiO2-capped n-Ge to lower its Schottky barrier height.

In this Letter, NiGe/SiO2/n-Ge ohmic contacts were demonstrated with Ge, rather than Ni, diffusion through the ion-implanted SiO2 films to form NiGe. The equivalent Schottky barrier height reduced from 0.58 eV for NiGe/n-Ge to ohmic contact. The anomalous diffusion behavior and accumulation of Ge in the SiO2 near the NiGe/SiO2 interface can be explained by vacancy-enhanced Ge diffusion. It is proposed that the presence of vacancies and Ge atoms embedded in the SiO2 layer play a significant role in the current enhancement by generation of multiple levels in the SiO2 band gap. [ABSTRACT FROM AUTHOR]