  GaSb/InAs heterojunction tunnel field-effect transistors are strong
candidates in building future low-power integrated circuits, as they could
provide both steep subthreshold swing and large ON-state current
($I_{\rm{ON}}$). However, at short channel lengths they suffer from large
tunneling leakage originating from the small band gap and small effective
masses of the InAs channel. As proposed in this article, this problem can be
significantly mitigated by reducing the channel thickness meanwhile retaining a
thick source-channel tunnel junction, thus forming a design with a non-uniform
body thickness. Because of the quantum confinement, the thin InAs channel
offers a large band gap and large effective masses, reducing the ambipolar and
source-to-drain tunneling leakage at OFF state. The thick GaSb/InAs tunnel
junction, instead, offers a low tunnel barrier and small effective masses,
allowing a large tunnel probability at ON state. In addition, the confinement
induced band discontinuity enhances the tunnel electric field and creates a
resonant state, further improving $I_{\rm{ON}}$. Atomistic quantum transport
simulations show that ballistic $I_{\rm{ON}}=284$A/m is obtained at 15nm
channel length, $I_{\rm{OFF}}=1\times10^{-3}$A/m, and $V_{\rm{DD}}=0.3$V. While
with uniform body thickness, the largest achievable $I_{\rm{ON}}$ is only
25A/m. Simulations also indicate that this design is scalable to sub-10nm
channel length.

Mesoscale and Nanoscale Physics