Electronically tunable Z-scheme GaS/AlSb heterojunction and its optical properties

This work investigates the geometric structure, electronic and optical properties of the GaS/AlSb van der Waals heterojunction (vdwH) using first-principles density functional theory (DFT) calculations. The investigation reveals that the pristine GaS/AlSb heterojunction, featuring a 3.40 Å interlayer distance, exhibits the utmost structural stability. Furthermore, this junction displays a narrowed band gap in comparison to its constituent monolayers, thereby facilitating the efficient generation and excitation of photogenerated carriers. The heterojunction belongs to the Z-scheme heterojunction in Type-II, which is more conducive to the enhancement of the redox capability of the heterostructure. The GaS/AlSb heterojunction has a higher Ultraviolet Rays (UV) absorption coefficient, which is valuable for applications in the field of UV photodetectors. Upon the application of both an electric field and strain to the GaS/AlSb van der Waals heterostructure (vdwH), it is found the band gap size of the heterojunction, and the direction of electron transfer can be effectively regulated. The light absorption coefficient and absorption range of heterojunctions can be improved to some extent by applying external strains, which can effectively improve the optical performance of the heterojunction. This study can provide a theoretical basis for the application of GaS/AlSb vdwH in future optoelectronic devices.