Optoelectronic properties of bilayer van der Waals WSe2/MoSi2N4 heterostructure：A first-principles study

Suitable bandgap semiconductors, especially those with the superb optical property and high carrier mobility as well as tunable electronic property, are of great significance for the development of optoelectronic devices. In this paper, we construct a vertical bilayer WSe2/MoSi2N4 van der Waals heterostructure (vdWH) and systematically investigate its crystal structure, stability and optoelectronic properties by first-principles calculations. Firstly, we find that the stable WSe2/MoSi2N4 bilayer is a type-I vdWH with the direct bandgap of 1.57 eV mainly determined by the component WSe2 monolayer. Furthermore, we show that the WSe2/MoSi2N4 vdWH has high mobility up to 104 cm2V−1s−1 and enhanced optical absorption compared to the isolated WSe2 and MoSi2N4 monolayers. More importantly, under the external electric field the WSe2/MoSi2N4 bilayer can form the tunable bandgap type-II vdWH, in which hole and electron can be effectively separated. Our findings not only provide a strategy for tailoring the electronic properties of two-dimensional MoSi2N4 material, but also have potential applications in optoelectronic devices.