  In this work, the source structure of an n-type thin-film tunneling FET is
engineered to get better performance. An ultra-thin SiGe along with Si is used
in the source of silicon-based TFET. Two structures are compared with
conventional TFET, one, SiGe is located on the top of Si in the source and
another one in reverse. Simulations approve these structures can reduce
sub-threshold swing, OFF-current several times, and increase the ON-OFF ratio.
Band diagram for conduction and valance bands are investigated and band to band
tunneling (BTBT) generation rate is used to find better performance. We find
current flows at Si in the source with the wider bandgap. Ge mole fraction of
SiGe is varied and its effects on the performance of TFET are studied. The SiGe
thickness for both structures is explored to obtain the best thickness for
SiGe.
