Quantum Mechanical Electrostatics and Transport Simulation and Performance Evaluation of Short Channel Monolayer WSe2 Field Effect Transistor
The device structure considered in this work is the nFET version of the device fabricated by Fang et al.  which has a 0.7 nm thick monolayer WSe2 channel of length 9.4 μm deposited on a 270 nm thick layer of SiO2. A 17.5 nm thick layer of ZrO2 served as the top oxide of the device (Figure 1). To model the monolayer WSe2 channel FET, we used band structure and material parameters available in the literature from first principle DFT simulations of Monolayer WSe2 sheets which have been listed in table I.
In this work, 1D Schrodinger-Poisson equations have been solved self-consistently along the direction perpendicular to the channel to get the C-V characteristics of the device (Figure 2). Then, ballistic transport characteristics were obtained using Launder-Buttiker formulation. Figure 3 and 4 show the Id-Vds and transfer characteristics of the device respectively. The threshold voltage of the device was extracted as 1.1 V (Figure 5). The subthreshold slope was calculated to be 60.913 mV/dec (Figure 6), which is remarkably near to the theoretical lower limit of 60mv/dec.
Table II lists some of the performance parameters obtained from the transport simulation. The parameters indicates that monolayer WSe2 FET has a very high on-off current ratio (~108), which makes it suitable for low power applications. The threshold voltage is found to be 1.1V for this undoped monolayer WSe2 channel which can be tuned by changing doping profile and physical dimensions of the device.
In this work we have a developed a simulator to study the electrostatics and quantum transport of monolayer WSe2 FET and extracted the performance parameters of that device. The developed simulator can be extended to calculate the ultimate performance limit and study the effects of different physical parameter variation on the performance of the device.
 Fang et al, Nano letters, 12(7), pp. 3788-3792 (2012).
 Yoon et al., Nano letters, 11(9), pp. 3768–3773 (2011).
 Kang et al., IEDM’12, p. 407-410 (2012).
 Chen et al, APL Materials 2, p. 092504 (2014).
 Zhao et al., ACS Nano, 8 (10), pp 10808–10814 (2014).
 Tosun et al., ACS Nano, 8(5), pp. 4948–4953 (2014).
 Liu et al., ECS Transactions, 58 (7), pp. 281-285 (2013).