A Continuous Semianalytic Current Model for DG and NW TFETs

A continuous semianalytic I-V model is developed for double-gate (DG) and nanowire tunnel FETs (TFETs). At the core of the model is a gate-controlled channel potential that satisfies the source and drain boundary conditions. The band-to-band tunneling current is expressed in terms of Franz's two-band E(k) relation with 3-D density of states. Verified by numerical simulations, the model is capable of generating Ids-Vgs characteristics for any a given bandgap and channel length, based on which the guidelines for TFET scaling are derived. A methodology for evaluating different ION-IOFF characteristics, distinguished from the common practice of ION/IOFF ratio and SS slope, is employed. Ambipolar effect or channel-todrain tunneling is also covered by the model. The model has been applied to an example of GaSb-InAs DG TFET, to compare with published atomistic simulation results. Ids-Vds characteristics are also generated by building into the model the debiasing effect of channel charge in the linear region.