  We propose a Heterojunction Vertical Tunneling FET and show using
self-consistent ballistic quantum transport simulations that it can provide
very steep subthreshold swings and high ON current, thereby improving the
scalability of Tunnel FETs for high performance. The turn-on in pocket region
of the device is dictated by modulation of heterojunction barrier height. The
steepness of turn-on is increased because of simultaneous onset of tunneling in
the pocket and the region underneath and also due to contribution to current by
vertical tunneling in the pocket. These factors can be engineered by tuning
heterojunction band offsets.
