First principles study on optoelectronic properties of energetically stable Si/InS van der Waals heterobilayers

The combination of van der Waals heterostructures by stacking different kinds of two-dimensional structures is an effective method to design optoelectronic devices. In this work, the electronic and optical properties of vertically stacked Si/InS heterostructures are investigated by using density functional theory. We check the dynamical stability of all possible bilayer configurations of Si/InS and only stable stackings are taken into account for the analysis of electronic and optical properties. The stacking-dependent band structures are calculated together with their alignment by regarding the contribution of layers that construct the heterostructure. The band alignment of the heterobilayer systems suggests type-I and type-II heterostructure formation according to their stacking pattern. The charge transfer between layers and work function of heterobilayers is also analyzed. We find that the Si/InS heterostructure forms an n-type Schottky contact with stacking-dependent Schottky barrier height of similar to 0.6-0.06 eV. Moreover, the effects of the perpendicular electric field were investigated on the electronic properties of Si/InS heterobilayers. Furthermore, it is shown that Schottky barrier height can be efficiently tuned by the variation of external electric field. The Si/InS heterostructure keeps a n-type Schottky contact for the all electric field values whereas the magnitude and the direction of the electric field enable the possibility of transformation between Schottky contact and ohmic contact at the Si/InS interface. Finally, the optical properties of Si/InS are also examined as part of density functional theory calculations by considering the imaginary part of the dielectric function. Here it is shown that absorption spectrum strongly depends on the stacking patterns of Si/InS heterostructure and these structures include strong prominent absorption peaks over the infrared and ultraviolet range. These results presented that Si/InS bilayer heterostructures may provide helpful information for the design and the fabrication of silicene-based two-dimensional van der Waals heterostructures that can be good candidates for tunable optoelectronics applications.