  We present a TCAD compatible multiscale model of phonon-assisted band-to-band
tunneling (BTBT) in semiconductors, that incorporates the non-parabolic nature
of complex bands within the bandgap of the material. This model is shown
capture the measured current-voltage data in silicon, for current transport
along the $[100]$, $[110]$ and $[111]$ directions. Our model will be useful to
predict band-to-band tunneling phenomena to quantify on and off currents in
Tunnel FETs and in small geometry MOSFETs and FINFETs.
