Tunnel-FET Evolution and Applications for Analog Circuits

Abstract

In this work different generations of field effect tunneling transistor (TFET) are evaluated through DC digital and analog figures of merits. For TFET devices the main digital figure of merit is the subthreshold slope (SS), while for analog application the intrinsic voltage gain (A_V) is the most important one. For the early generations, that are based on silicon, the SS does not reach values smaller than 60mV/dec at room temperature, however, the A_V reaches values up to 80 dB, showing to be promising for analog applications. As the TFETs were being optimized for digital applications and consequently presenting better switching performance, the intrinsic voltage gain moves in the opposite direction. This opposite trend is related to which transport mechanism is predominant for each type of device. While III-V TFETs are more dependent on Band to Band Tunneling (BTBT), silicon devices are more relying on Trap-Assisted Tunneling (TAT). While BTBT allows for faster switching, TAT is less dependent on the drain electric field, so the former favors SS while the latter favors A_V. Based on the good analog behavior of silicon channel TFETs, a two-stage operational transconductance amplifier (OTA) was designed with different TFET technologies and the compared results were discussed.