Effects of vertical strain and electrical field on electronic properties and Schottky contact of graphene/MoSe2 heterojunction

Fabricating a low Schottky barrier is still a great challenge in electrical transport behavior of nano field effect transistors (FETs). To settle this problem, the electronic properties and Schottky contact of the graphene/MoSe2 heterojunction employing various vertical strains and external electrical fields are investigated with density functional theory (DFT) to obtain low Schottky barrier. Our calculation illustrates that in the graphene/MoSe2 heterojunction, the intrinsic electronic properties of components are well preserved owing to the weak van der Waals (vdW) mutual interaction between graphene and MoSe2 monolayer. Furthermore, there is an n-type Schottky contact formed with an n-type Schottky barrier height (SBH) of 0.56 eV at the interface of graphene/MoSe2 heterojunction. It is worth noting that the type and the height of Schottky barrier are susceptible to the external electrical field or strain employed perpendicularly to the graphene/MoSe2 heterojunction. And the SBH of the interface can be reduced by tuning the interlayer distance (d) or the electrical field intensity (E). Moreover, Schottky contact transforms from n-type to p-type at d = 3.22 Å or E = +0.08 V/Å. Additionally, the Ohmic contact occurs when the magnitude of positive or negative electrical field is larger than 0.40 V/Å, respectively. Additionally, the heterojunction maintaining high carrier mobility is inferred from the effective masses of electron and hole, namely, 0.074 m0 and 0.055 m0, respectively. Our study may put forward effective strategies to enhance the electronic performance of MoSe2-based vdW heterojunction FETs.