Vertically Extended Drain Double Gate Si1−xGex Source Tunnel FET : Proposal & Investigation For Optimized Device Performance

Abstract

This paper reports an unique approach to suppress ambipolarity and enhance drive current in tunnel field effect transistor (TFET) by incorporating vertically extending drain in double gate Si1−xGex source TFET. This structure has dual source extending laterally on both sides of the channel with vertically extended drain over the T-shaped channel (VD-DG-Si1−xGexS-TFET). Our study is based on calibrated exhaustive 2-D TCAD simulations. It advocates that the device performance is not only retained but significantly enhanced even by deploying only double gate instead of quadruple gate with Si1−xGex sources. Further the drive current can be significantly increased by optimizing the mole fraction (x) in Si1−xGex source. Our study reveals that the average subthreshold slope (SSavg) is 23.98 m V/dec (point SS (SSpoint) is 12.7 m V/dec with sub-60 m V/dec point SS for 107 orders of current change), drive current (ION) is 2.73× 10− 4 A/um and 46% improvement in transconductance as compared to the earlier reported drain engineered quardruple gate TFET. Further the device sensitivity analysis with respect to gate oxide dielectric constant, gate metal work-function, temperature and germanium mole fraction variation is also analyzed here. Moreover, in terms of device analog behaviour, the cut off frequency (ft) is reported as 38.93 GHz and 140% increment in gain bandwidth product (GWB) as compared to its quardruple gate alternative. This study proves the potentials of considered device structure as a promising candidate for ultra low power analog/RF and digital logic applications.