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

Novel strain-engineered staggered gap Ge/InxGa1-xAs 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× and 16.9× enhancement in I_ON for n- and p-channel Ge/In_xGa_1-xAs 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_xGa_1-xAs/n⁺-In_xGa_1-xAs) exhibited superior leakage suppression due to a larger tunneling barrier at the channel-drain interface. Moreover, the p-type H-TFETs (n⁺-In_xGa_1-xAs/i-Ge/p⁺-Ge) demonstrated a significant enhancement in I_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_xGa_1-xAs 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.