Intrinsic Electron and Hole Transport in Channel Passivated WSe$_{2}$ Field-Effect Transistors with Graphene Contacts*

We report electrical transport measurement of high-quality WSe$_{2}$ field-effect transistors. As a nearly intrinsic semiconductor with a relatively large bandgap, WSe$_{2}$ tends to form substantial Schottky barriers with common contact metals for both electron and hole channels, which obstructs the charge injection especially at low temperatures. In this work, we use highly n- and p-doped graphene as an electrode material to form low resistance electrical contacts to the electron and hole channels, respectively. To minimize surface and interface scattering, hexagonal boron nitride was used to passivate both the top and bottom surfaces of the WSe$_{2}$ channel. Four-terminal transport measurement was carried out for a wide temperature range to understand the intrinsic transport properties of atomically thin WSe$_{2}$. Field-effect mobility and effective mobility for both electron and hole channels as well as their temperature dependence will be discussed.