Tunable electronic and optical properties of WSe2/Si2H heterojunction via electric field

Abstract Van der Waals heterojunctions based on two-dimensional (2D) materials hold great potential applications in photodetectors. Using the density functional theory (DFT) method, the structures, electronic and optical properties of van der Waals WSe 2 /Si 2 H heterojunction are investigated. 1.32 eV of indirect bandgap is calculated from the WSe 2 /Si 2 H heterojunction, which is 0.3 eV and 0.1 eV smaller than those of its monolayer WSe 2 and Si 2 H. This contributes to the photocarrier generations, and the Type-II heterojunction also benefits to the separation of the photogenerated electron and hole pairs. A significant hole mobility 1.05 × 10 4 cm 2 V −1 s −1 of the heterojunction along the y-direction is obtained. Moreover, a high Ultraviolet light (UV) absorption coefficient is presented in the heterojunction. The heterojunction transforms to Type-I under a vertical electric field, with the bandgap, orientation and amount of transfer electrons modulated sufficiently. As a result, the optical absorption coefficient of the heterojunction is also improved significantly, leading to the red-shift of the absorption spectrum. These excellent properties address the WSe 2 /Si 2 H heterojunction one of the good candidates for UV detectors.