Valley Resolved Current Components Analysis of Monolayer TMDFETs

After silicon, semiconducting 2D transition metal dichalcogenide monolayers (TMDs) crystals are coming up as favorable candidate in ultra-thin channels material in the future generation of transistors. However, fabrication of these crystals as channel materials with acceptable performance is still challenging. Presence of direct bandgaps (1-2eV) in monolayer semiconducting TMDs, along with mobility improvement by dielectric engineering, It opens up a boundless scope in future electronic applications. In present work, we give a computational study on contribution of the second-lowest valley (Q valley about midway between K and Γ) of conduction band on device performance in monolayer TMD based MOSFETs (TMDFETs). From our calculation, we have found that the contribution of Q valley is not negligible, as the energy difference between conduction band minima (CBM) and second lowest valley (ΔEc) is very small and it is around 2kT. Q valley has valley degeneracy of 6, compared with valley degeneracy 2 for K Valley in the conduction band. So, we can say that the occupancy of `K' valley and `Q' valley is very close to each other. Hence two valleys are equally important for carrier transport. In our studies, we have found, the contribution of the second-lowest valley of all semiconducting monolayer TMDs in the current calculation is very significant.