  Two dimensional materials such as Transition Metal Dichalcogenides (TMDC) and
their bi-layer/tri-layer heterostructures have become the focus of intense
research and investigation in recent years due to their promising applications
in electronics and optoelectronics. In this work, we have explored device level
performance of trilayer TMDC heterostructure (MoS2/MX2/MoS2; M=Mo or, W and X=S
or, Se) Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) in the
quantum ballistic regime. Our simulation shows that device 'on' current can be
improved by inserting a WS2 monolayer between two MoS2 monolayers. Application
of biaxial tensile strain reveals a reduction in drain current which can be
attributed to the lowering of carrier effective mass with increased tensile
strain. In addition, it is found that gate underlap geometry improves
electrostatic device performance by improving sub-threshold swing. However,
increase in channel resistance reduces drain current. Besides exploring the
prospect of these materials in device performance, novel trilayer TMDC
heterostructure double gate Field Effect Transistors (FETs) are proposed for
sensing Nano biomolecules as well as for pH sensing. Bottom gate operation
ensures these FETs operating beyond Nernst limit of 59 mV/pH. Simulation
results found in this work reveal that scaling of bottom gate oxide results in
better sensitivity while top oxide scaling exhibits an opposite trend. It is
also found that, for identical operating conditions, proposed TMDC FET pH
sensors show super-Nernst sensitivity indicating these materials as potential
candidates in implementing such sensor. Besides pH sensing, all these materials
show high sensitivity in the sub-threshold region as a channel material in
nanobiosensor while MoS2/WS2/MoS2 FET shows the least sensitivity among them.
