Scalable GaSb/InAs Tunnel FETs With Nonuniform Body Thickness

GaSb/InAs heterojunction tunnel FETs are strong candidates in building future low-power ICs, as they could provide both steep subthreshold swing and large on-state current (I
_ON
). However, at short-channel lengths, they suffer from large tunneling leakage originating from the small bandgap and small effective masses of the InAs channel. As proposed in this paper, 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 nonuniform body thickness. Because of the quantum confinement, the thin InAs channel offers a large bandgap 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
_ON
. Atomistic quantum transport simulations show that ballistic I
_ON
= 284 A/m is obtained at 15-nm channel length, I
_OFF
= 1 × 10
^-3
A/m, and V
_DD
= 0.3 V, while with uniform body thickness, the largest achievable I
_ON
is only 25 A/m. Simulations also indicate that this design is scalable to sub-10-nm channel length.