A Tunnel FET for VDD Scaling Below 0.6 V With a CMOS-Comparable Performance

Abstract

We propose a modified structure of tunnel field-effect transistor (TFET), called the sandwich tunnel barrier FET (STBFET). STBFET has a large tunneling cross-sectional area with a tunneling distance of ~2 nm. An orientation-dependent nonlocal band-to-band tunneling (BTBT) model was employed to investigate the device characteristics. The feasibility of the STBFET realization using a complementary metal-oxide-semiconductor-compatible process flow has been shown using advanced process calibration with Monte Carlo implantation. STBFET gives a high I ON , exceeding 1 mA/μm at I OFF of 0.1 pA/μm with a subthreshold swing below 40 mV/dec. The device also shows better static and dynamic performances for sub-1-V operations. STBFET shows a very good drain current saturation, which is investigated using an ab initio physics-based BTBT model. Furthermore, the simulated I ON improvement is validated through analytical calculations. We have also investigated the physical root cause of the large voltage overshoot of TFET inverters. The previously reported impact of Miller capacitance is shown to be of lower importance; the space-charge buildup and its relaxation at the channel drain junction are shown to be the dominant effect of large voltage overshoot of TFETs. The STBFET are shown to have negligible voltage overshoots compared with conventional TFETs.