Electronic and optical characteristics of GaS/g-C3N4 van der Waals heterostructures: Effects of biaxial strain and vertical electric field

The electronic and optical characteristics of GaS/g-C3N4 van der Waals (vdWs) heterostructures were studied using density functional theory based on first-principles. The GaS/g-C3N4 vdWs heterostructures with different structural configurations were compared with their formation energies, and their stability was proved by computational molecular dynamics. The stable GaS/g-C3N4 vdWs heterostructures has an indirect band gap semiconductor with a type-I band alignment. Bader charge research demonstrates that GaS is the electron acceptor and g-C3N4 is the electron-donor. The effects of biaxial strain and vertical electric field on electronic and optical properties were analyzed. Both biaxial strain and vertical electric fields can adjust values of band offset and band gaps. Interestingly, when biaxial strain and vertical electric fields are applied, GaS/g-C3N4 vdWs heterostructures has mutual transformation from type-I to type-II band alignment. The type-II band alignment is a feasible scheme in the study of photocatalysis, photocell and photovoltaic. Moreover, the GaS/g-C3N4 vdWs heterostructure with biaxial strain has a strong absorption peak in the visible light region, which is conducive to the photocatalysis of visible light. The results show that the GaS/g-C3N4 vdWs heterostructure has huge application potential in the fields of optoelectronic devices and photocatalysis.