2D full-band, Atomistic Quantum transport in L-shaped Vertical InSb/InAsn-TFETs

Abstract

In the present work, we have investigated the performances of L shaped Vertical broken bandgapheterostructureInSb InAsn-channel tunnel field effect transistors TFETs of 4 nm thin channel structures with the gate lengths of 20nm. We have used a 3D full band, quantum mechanical simulator based on atomistic sp3d5s spin-orbital coupled tight binding method.In this L shaped nonlinear geometry the gate electric field and tunnel junction internal field are oriented in same direction. A broken narrow bandgap BG structure has another advantage that transport is by mixture of electrons holes. TFETs are promising devices for lowpower logic design due to low subthreshold swing SS and high Ion Ioff ratio. We investigate current voltage characteristics, ON current OFF current andsubthreshold swing as function of equivalent oxide thickness, gate length, drain length, gate undercut, High K, and drain thicknessfor L shaped nonlinear geometry tunnel FET for low subthreshold swing and lowvoltage operation. To study 2D electronic transport in this L shaped nonlinear geometry we used Non Equilibrium Green Function NEGF based quantum transport method using sp3d5s tight binding model in which Poisson-Schr odinger solver self consistently iterates to obtain potentials and Local Density of States LDOS. The advantage of this method is that it can handle arbitrary geometries and complicated 2D structures like Band to Band tunnelling BTBT devices. NEGF quantum transport method gives output in terms of Poisson potential and space charge in 3D, energy resolved transmission and spectral function and Local Density of States of electrons holes in space and energy.