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

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 ∼5 × 10 7 and ∼3 × 10 6 , respectively. The remarkably low off current density is 2.1 µA/cm 2 for p + -Ge/n-Si and 19 µA/cm 2 for n + -Ge/p-Si at a reverse bias of | V R |=±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 | V F |=±1 V is obtained with a GeO 2 passivation and an Al 2 O 3 isolation.