Stacking Order-Dependent Electronic, Optical, and Charge Transport Properties of van der Waals GaS/WXY (X/Y = S, Se, Te) Heterostructures

The introduction of Janus transition-metal dichalcogenide (TMD) monolayers is expected to bring fascinating properties into van der Waals (vdW) heterostructures. Hence, we investigate the electronic, optical, and charge transport properties of GaS/WXY (X/Y = S, Se, Te) vdW heterostructures using first-principles calculations and nonequilibrium Green's function methods. When the Janus monolayer is flipped upside-down, its stacking order changes from GaS/SWSe to GaS/SeWS, resulting in the reversal of the direction of the out-of-plane dipole moment. Our results clearly show that the interlayer coupling determined by the stacking order is negatively correlated with the electron mobility of the system. Among them, GaS/SWSe and GaS/TeWSe, respectively, possess the largest and the smallest electron mobility of about 2.1 × 104 and 3 × 102 cm2/Vs. We further reveal the effect of in-plane strain on the electronic structure of different stacking orders. At the critical strain, the band alignment type is changed and the optical absorption coefficient is enhanced. Our work lays the theoretical foundation for selectively building the stacking order and new means of regulating interface interactions and provides a new platform for designing high-performance electronic and optoelectronic devices.