  This paper projects the enhanced drive current of a n-type electrostatically
doped (ED) tunnel field-effect transistor (ED-TFET) based on heterojunction and
band-gap engineering via TCAD 2-D device simulations. The homojunction ED-TFET
device utilizes the electrostatic doping in order to create the source/drain
region on an intrinsic silicon nanowire that also felicitates dynamic
re-configurability. The ED-TFET offers good electrostatic control over the
channel with reduced thermal budget and process complexity. However, device
exhibits low ON current, therefore, in this work, we elaborate on interfacing
of group III-V with group IV semiconductors for heterojunction. Incorporation
of heterojunction and band gap engineering in the ED-TFET has improved drive
current even at very low operating voltage. The comparison of various low band
gap source region materials shows that germanium (Ge) source (Si-Si-Ge) ED-TFET
provides steepest subthreshold swing (SS) of about 9.5 mV/dec, and higher
ON-state drive current of 1.58 mA at $V_{DS}$ = 1 V and 0.093 mA at $V_{DS}$ =
0.5 V with same SS.
