STUDY AND PHYSICS BASED MODELLING OF TFET

Abstract

Demand for low power operating devices imposed by the mobile, portable electronics and the current chip market has been the motivational source for the researchers for many years. Although circuit and system engineers have put their efforts to reduce the power, but still the fundamental limit in the overall energy efficiency of a system is still rooted in the Metal-Oxide- Semiconductor Field Effect Transistor (MOSFET) physics i.e. an injection of thermally distributed carriers which does not allow the switching characteristics better than 60 mV/dec at room temperature which puts a constraint over the scaling of supply voltage Vdd and lowest t energy consumed per digital operation with current CMOS technology. In this work, Tunnel-Field-Effect-Transistor (TFET) based on gate induced band-to-band tunneling is studied as an alternative device to overcome the physical limit of the subthreshold slope in MOSFETs which permit the scaling of supply voltage (VDD) and lower threshold (VTH) operation. Following introducing the working principle of the TFET, the calibrated Technology Computer Aided Design (TCAD) simulations are used to study the behavior of the carriers inside the channel to get an overview of the deep physics associated with it. After filtering the existing analytical models for TFET on-current, various areas are explored which required to be improved. As similar to subthreshold current in MOSFETs, the study of leakage current called "sub onset current" (sub onset is the point where the overlapping of valence and conduction bands starts) in TFET is also important from the digital application point of view. Keeping this in mind, a SRH generation and recombination based model is proposed for the physical modeling of sub onset current. I