Exploration and Exploitation of Strain Engineering in 2D-FETs.

Two-dimensional (2D) van der Waals semiconductors, especially transition-metal-dichalcogenides (TMDs), have emerged as prospective channel materials for sub-10 nm channel length ( $L_{CH}$ ) FETs due to their superior scalability and low-power characteristics arising from their large bandgap, suitable effective mass ( $m^{\ast}$ ), atomic-scale thickness, and pristine interfaces, w.r.t conventional (bulk) semiconductors such as silicon [1]. Considering the performance enhancements observed in state-of-the-art Si-MOSFETs via strain engineering [2], it is fruitful to explore if such strain engineering can be exploited to enhance the performance of 2D-FETs, by modulating $m^{\ast}$ and density-of-states (DOS) of the 2D-TMDs. Although some preliminary work in this direction have shown modulation of mobility for a few TMDs [3] or ballistic transport for a single TMD [4], a more detailed study incorporating dissipative transport to accurately determine current [1] is missing, which by providing new insights into the strain engineering of such 2D-TMDs can enable 2D-FETs to attain their full potential in the near future. In this work by employing density-functional-theory (DFT) simulations and non-equilibrium Green's function (NEGF) transport formalism [1], we study the effects of various types of strain on the material properties of TMDs (specifically MoX 2 and WX 2 where $\mathrm{X} =\mathrm{S}$ , Se, Te) and Black phosphorus (BP) (which has anisotropic $m^{\ast}$ [5]), followed by evaluating the mobility (incorporating intrinsic-phonon, charge impurity, and remote-phonon scatterings [6], [7]) and finally, for the first time, simulate realistic dissipative transport to investigate the merits of strain engineering in an actual device.