Tunable Electronic Properties of Type-II SiS/WSe Hetero-Bilayers.

First-principle calculations based on the density functional theory (DFT) are implemented to study the structural and electronic properties of the SiS/WSe hetero-bilayers. It is found that the AB-2 stacking model is most stable among all the six SiS/WSe heterostructures considered in this work. The AB-2 stacking SiS/WSe hetero-bilayer possesses a type-II band alignment with a narrow indirect band gap (0.154 eV and 0.738 eV obtained by GGA-PBE and HSE06, respectively), which can effectively separate the photogenerated electron-hole pairs and prevent the recombination of the electron-hole pairs. Our results revealed that the band gap can be tuned effectively within the range of elastic deformation (biaxial strain range from -7% to 7%) while maintaining the type-II band alignment. Furthermore, due to the effective regulation of interlayer charge transfer, the band gap along with the band offset of the SiS/WSe heterostructure can also be modulated effectively by applying a vertical external electric field. Our results offer interesting alternatives for the engineering of two-dimensional material-based optoelectronic nanodevices.