Optimum Bandgap and Supply Voltage in Tunnel FETs

A physics-based analytic model of the ON- and OFF-currents in a homojunction tunnel field-effect transistor (TFET) is used to understand the relationship between bandgap, gate length, ON-current, OFF-current, ON/OFF current ratio, and supply voltage to meet minimum energy requirements. The model, which applies to direct-bandgap semiconductors, is validated against numerical simulations to show that it captures the trends of more comprehensive simulations. The analytic model is then used to compare alternative channel materials for TFETs. Gate-all-around InAs nanowire and graphene nanoribbon TFETs are used as design examples at gate lengths of 10 and 15 nm and for an ON/OFF current specification of 10⁵. The results suggest that TFETs based on 2-D materials can be more energy efficient than semiconductor nanowire TFETs and conventional metal-oxide-semiconductor field-effect transistors for low-power logic.