On the Static and Dynamic Behavior of the Germanium Electron-Hole Bilayer Tunnel FET

Abstract

Tunnel FETs (TFETs) are being intensively investigated for their potential in achieving subthermal switching slopes and extremely low leakage currents. Recently, a promising concept has been proposed: the electron-hole bilayer TFET (EHBTFET), which exploits carrier tunneling through a bias-induced electron-hole bilayer. In this paper, we show that, through appropriate optimization of the Ge EHBTFET, it is possible to achieve superior static characteristics at low supply voltages, when compared with a double-gate Ge MOSFET with similar geometry. The EHBTFET provides an improved average subthreshold slope (from 0 to |V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DD</sub> | = 0.25 V) of 30 mV/dec against 60 mV/dec at same |I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> | ~ 0.18 μA/μm, doubled inverter gain, and larger noise margins, suggesting great potential for low-power applications. The dynamic behavior of the devices is investigated by transient simulations of simple circuits based on complementary inverters. Due to the increased total EHBTFET capacitance, the fanout-of-1 delay is larger than that in MOSFET, with 11 ns versus 4 ns at |V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DD</sub> | = 0.25 V. However, the EHBTFET results to be more robust than MOSFET for voltage scaling, as the leakage component is far from approaching the dynamic component of the total switching energy at low V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DD</sub> .