Area equivalent WKB Compact modeling approach for tunneling probability in Hetero-Junction TFETs including ambipolar behaviour

This paper introduces an innovative modeling approach for calculating the band-to-band (B2B) tunneling probability in tunnel-field effect transistors (TFETs). The field of application is the usage in TFET compact models. Looking at a tunneling process in TFETs, carriers try to tunnel through an energy barrier which is defined by the device band diagram. The tunneling energy barrier is approximated by an approach which assumes an area equivalent (AE) triangular shaped energy profile. The simplified energy triangle is suitable to be used in the Wentzel-Kramers-Brillouin (WKB) approximation. Referring to the area instead of the electric field at individual points is shown to be a more robust approach in terms of numerical stability. The derived AE approach is implemented in an existing compact model for double-gate (DG) TFETs. In order to verify and show the numerical stability of this approach, modeling results are compared to TCAD Sentaurus simulation data for various sets of device parameters, whereby the simulations include both ON- and AMBIPOLAR-state of the TFET. In addition to the various device dimensions, the source material is also changed to demonstrate the feasibility of simulating hetero-junctions. Comparing the modeling approach with TCAD data shows a good match. Apart the limitations demonstrated and discussed in this paper, the main advantage of the AE approach is the simplicity and a better fit to TCAD data in comparison to the quasi-2D WKB approach.