Electronic and optical properties of the GeS/GeSe heterostructure tuned by in-plane strain

Abstract

Constructing new two-dimensional (2D) van der Waals (vdW) heterostructures has been widely employed as a convenient and effective strategy for tuning the optoelectronic properties, which is of great significance for applications in integrated nano-optoelectronic devices. In this work, we design a GeS/GeSe vdW heterostructure and systematically investigate its electronic and optical properties by using first-principles calculations. Our results indicate that the pristine GeS/GeSe heterostructure possesses an indirect band gap (∼0.98 eV) and exhibits an intrinsically type-I band alignment. Furthermore, the optoelectronic properties of the GeS/GeSe heterostructure can be effectively modulated by applying in-plane strain. Specifically, an indirect to direct band gap transition and a type-I to type-II band alignment transition can be synchronously realized, when the tensile strain along zigzag direction reaches 2%. Furthermore, the calculated dielectric function also reveals an obvious strain effect on the optical properties of the GeS/GeSe heterostructure. The light absorption coefficient of the GeS/GeSe heterostructure along the zigzag direction can reach to 106 cm−1 level, as the compressive in-plane strain reaches −5%. These findings are expected to play a guidance role in the future design of the optoelectronic devices based on 2D anisotropic heterostructures.