Promising Photoelectronic Properties of Two-Dimensional MoSi₂N₄/WS₂ Heterojunction: A First-Principles Study

In this paper, the design of a two-dimensional MoSi₂N₄/WS₂ van der Waals heterojunction (vdWH) and its optoelectronic device are reported. First-principles calculations predicted that the MoSi₂N₄/WS₂ vdWH exhibits a direct band gap, with electron mobility reaching 8431 cm² V^–1 s^–1, and its light absorption coefficient is 14 × 10⁵ and 4 × 10⁵ cm^–1 in the ultraviolet and visible regions, respectively. By employing the nonequilibrium Green’s function method, the proposed two-probe device based on the MoSi₂N₄/WS₂ vdWH has a responsivity of 0.229 A W^–1 and an external quantum efficiency of 73.2%. It is also predicted that the peak photocurrent of MoSi₂N₄/WS₂ vdWH in the ultraviolet region is 35 nA/nm. The present results show that the two-dimensional MoSi₂N₄/WS₂ vdWH has great application potential in photodetector devices.