Strain and electric field modulated electronic structure of two-dimensional SiP(SiAs)/GeS van der Waals heterostructures

Abstract

The van der Waals (vdW) heterostructures that combine different two-dimensional (2D) materials can effectively improve the electronic and optical properties. Recently, the group-IV monochalcogenide GeS, as a potential candidate material for vdW heterostructures, has attracted much attention due to its puckered structure and unique electronic properties. However, the indirect band gap of GeS limits its applications in electronic devices. Here, the electronic structure of 2D SiP(SiAs)/GeS heterostructures is investigated systematically by first-principles calculations. The typical type-II band alignment appears in the SiP(SiAs)/GeS heterostructures, which can effectively facilitate the separation of photogenerated electron and hole pairs. Especially, the SiAs/GeS vdW heterostructure shows a direct band gap of 0.953 eV, which makes it have potential applications in optoelectronic devices. Additionally, by increasing or decreasing the interlayer distance, the binding energy of the heterostructure increases, where the charge transfer can be modulated. Furthermore, the charge transfer, band gap and band offset of the heterostructures are sensitive to the in-plane strain. Moreover, the large band offset at a positive electric field can enhance the photogenerated charge separation when the SiP(SiAs)/GeS heterostructures are irradiated with light. These calculated results indicate that the SiP(SiAs)/GeS vdW heterostructures are good candidates for low-dimensional optoelectronic devices.