Performance Comparison of Silicon Steep Subthreshold FETs

In the last few decades, MOSFET scaling has enabled smaller and faster transistors that consume less power per operation. However, as device dimensions were shrunk into the sub-65-nm regime, nonscalability of the subthreshold swing to below 60 mV/dec has resulted in a significant increase in off-state current and standby power dissipation. The impact ionization FET, p-i-n and p-n-p-n tunnel FET, feedback FET, and nanoelectromechanical FET were proposed as novel device concepts that achieve sharper swings than 60 mV/dec. As a result, these devices potentially enable reduced operation and considerable reduction in system power. In this paper, a detailed comparison of these steep subthreshold devices in terms of speed and power is presented, and the challenges for each device to become a viable MOSFET alternative are outlined.