Field-effect transistors of high-mobility few-layer SnSe$_{2}$

Abstract

We report the transport properties of mechanically exfoliated few-layer SnSe$_{2}$ flakes, whose mobility is found with four probe measurements to be ~ 85 cm$^{2}$V$^{-1}$s$^{-1}$ at 300 K, higher than those of the majority of few-layer transitional metal dichalcogenides (TMDs). The mobility increases strongly with decreased temperature, indicating a phonon limited transport. The conductivity of the semiconducting SnSe$_{2}$ shows a metallic behavior, which is explained by two competing factors involving the different temperature dependence of mobility and carrier density. The Fermi level is found to be 87 meV below the conduction band minima (CBM) at 300 K and 12 meV below the CBM at 78 K, resulting from a heavy n-type doping. Previous studies have found SnSe$_{2}$ field-effect transistors (FETs) to be very difficult to turn off. We find the limiting factor to be the flake thickness compared with the maximum depletion width. With fully depleted devices, we are able to achieve a current on-off ratio of ~10$^{5}$. These results demonstrate the great potential of SnSe2 as a two dimensional (2D) semiconducting material and are helpful for our understanding of other heavily doped 2D materials.