Valley Resolved Current Components Analysis of Monolayer TMDFETs

Abstract

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.