Si–Ge Axial Heterojunction RFET With Enhanced On-State Current and Low Subthreshold Swing

This article investigates Si and Ge dual-gate reconfigurable field-effect transistors (DG-RFETs) at the nanoscale. It is found that while the Ge DG-RFET improves the ON-state saturated current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\textit{I}}_{\text{\biosc{on}}}$</tex-math></inline-formula>) of the Si DG-RFET, it also generates bipolar currents at low voltages, which increase as the device size decreases. By analyzing the conduction mechanism of the DG-RFET and examining the source of the bipolar currents in Ge DG-RFETs, we propose a silicon–germanium axial heterojunction RFET (Si–Ge AH-RFET). The conduction mechanism was investigated in detail by Sentaurus TCAD, which revealed a unique double-tunneling mechanism in the P-program. Simulation results show that compared with Si DG-RFETs, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\textit{I}}_{\text{\biosc{on}}}$</tex-math></inline-formula> of the proposed Si–Ge AH-RFET is improved by approximately eight times in the N-program and about 11 times in the P-program and the subthreshold swing (SS) is significantly reduced. Meanwhile, it does not exhibit the same bipolar currents at low voltages as the Ge DG-RFET and maintains the low leakage current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\textit{I}}_{\text{\biosc{off}}}$</tex-math></inline-formula>) as the Si DG-RFET. Furthermore, compared with the Si DG-RFET, the transmission delay of the Si–Ge AH-RFET-based inverter is reduced by approximately 75%.