Effects of Localized Body Doping on Switching Characteristics of Tunnel FET Inverters With Vertical Structures

In order to verify the effects of localized body doping (LBD) on alternating current switching performances of tunnel FETs (TFETs) with vertical structures, The TFET inverter composed of n-/p-type TFET with the localized p
⁺
/n
⁺
body doping is simulated with the help of mixed-mode device and circuit simulations. As a result, falling/rising delay is significantly improved due to the locally high channel-to-drain side energy barrier induced by the LBD. Furthermore, LBD conditions, such as doping concentration, depth, and width, are optimized to maximize the improvement of falling/rising delay. Based on the optimization results, it is found that enough wide doping width and deep depth are inevitable to minimize the drain voltage (VD)-induced lowering of the locally increased barrier and the increase of ambipolar current and too wide doping width cannot be applied due to the ON-current reduction caused by the degraded controllability of gate voltage on channel similarly to short channel effects. Moreover, the doping width and depth should be adjusted according to LBD concentration.