High On/Off Ratio and Very Low Leakage in p(+)/n and n(+)/p Germanium/Silicon Heterojunction Diodes

Abstract

We demonstrate the characteristics of p(+)-Ge/n-Si and n(+)-Ge/p-Si heterojunction diodes with a very high on/off ratio and very low leakage current using heteroepitaxial Ge grown directly on Si. The current ratio of p(+)-Ge/n-Si and n(+)-Ge/p-Si heterojunction is similar to 5 x 10(7) and similar to 3 x 10(6), respectively. The remarkably low off current density is 2.1 mu A/cm(2) for p(+)-Ge/n-Si and 19 mu A/cm(2) for n(+)-Ge/p-Si at a reverse bias of vertical bar V-R vertical bar = +/- 1 V, respectively. High on current density (125 A/cm(2) for p(+)-Ge/n-Si and 54 A/cm(2) for n(+)-Ge/p-Si) with a forward bias vertical bar V-F vertical bar = +/- 1 V is obtained with a GeO2 passivation and an Al2O3 isolation. (C) 2013 The Japan Society of Applied Physics