Performance Evaluation of Novel Strain-Engineered Ge-InGaAs Heterojunction Tunnel Field-Effect Transistors

Abstract

Novel strain-engineered staggered gap Ge/In x Ga1– x As heterojunction tunnel FETs (H-TFETs) are proposed and theoretically evaluated. Modulation of the indium alloy composition at the source–channel heterointerface resulted in $18.6\times $ and $16.9\times $ enhancement in $I_{\mathrm{\scriptscriptstyle ON}}$ for n- and p-channel Ge/In x Ga1– x As H-TFETs, respectively, as compared with strained Ge homojunction TFETs (p+-Ge/i-Ge/n+-Ge). The n-type H-TFETs (p+-Ge/i-In x Ga1– x As/n+-In x Ga1– x As) exhibited superior leakage suppression due to a larger tunneling barrier at the channel–drain interface. Moreover, the p-type H-TFETs (n+-In x Ga1– x As/i-Ge/p+-Ge) demonstrated a significant enhancement in $I_{\mathrm{\scriptscriptstyle ON}}$ due to an unequal shift in the conduction band edge as a result of doping-induced bandgap narrowing. The simulated tensile-strained Ge/In x Ga1– x As H-TFETs show a great promise for ultralow-power switches with high ON-state and low OFF-state current, providing a new path for low-power complimentary TFET logic.