  In this work, the transport of tunnel field-effect transistor (TFET) based on
vertically stacked hereto-structures from 2D transition metal dichalcogenide
(TMD) materials is investigated by atomistic quantum transport simulations.
WTe2-MoS2 combination was chosen due to the formation of a broken gap
hetero-junction which is desirable for TFETs. There are two assumptions behind
the MoS2-WTe2 hetero-junction tight binding (TB) model: 1) lattice registry. 2)
The $S-Te$ parameters being the average of the $S-S$ and $Te-Te$ parameters of
bilayer MoS2 and WTe2. The computed TB bandstructure of the hetero-junction
agrees well with the bandstructure obtained from density functional theory
(DFT) in the energy range of interest for transport. NEGF (Non-Equilibrium
Green$'$s Function) equations within the tight binding description is then
utilized for device transfer characteristic calculation. Results show 1) energy
filtering is the switching mechanism; 2) the length of the extension region is
critical for device to turn off; 3) MoS2-WTe2 interlayer TFET can achieve a
large on-current of $1000 \mu A/\mu m$ with $V_{DD} = 0.3V$, which suggests
interlayer TFET can solve the low ON current problem of TFETs and can be a
promising candidate for low power applications.
