In this work, we extend an already existing simulator for tunnel FETs to fully take into account nonparabolicity (NP) of the conduction band in all aspects, namely the wave-function (WF) and density of states (DOS) corrections for both charge and BTBT current calculation. Comparison against more advanced full-quantum simulators based on TB and k ·p Hamiltonians is presented as well and indicates very good matching between models for simple tunnel diodes. An initial parameter study of the Electron Hole Bilayer TFET (EHBTFET) indicates the presence of an optimum channel thickness, determined by the interplay between the subband alignment voltage and ON current level. © 2015 IEEE.