Low-pressure PVD growth SnS/InSe vertical heterojunctions with type-II band alignment for typical nanoelectronics

Two-dimensional (2D) polarization-sensitive detection as a new photoelectric application technology is extensively investigated. However, most devices are mainly based on individual anisotropic materials, which suffer from large dark current and relatively low anisotropic ratio, limiting the practical application in polarized imaging system. Herein, we design a van der Waals (vdWs) p-type SnS/n-type InSe vertical heterojunction with proposed type-II band alignment via low-pressure physical vapor deposition (LPPVD) and dry transfer method. The performance compared with the distinctive thickness of anisotropic SnS component was first studied. The fabricated device with a thick (80 nm) SnS nanosheet exhibits a larger rectification ratio exceeding 10³. Moreover, the SnS/InSe heterostructure shows a broadband spectral photoresponse from 405 to 1100 nm with a significant photovoltaic effect. Due to efficient photogenerated carrier separation across the wide depletion region at zero bias, the device with thinner (12.4 nm) SnS exhibits trade-off photoresponse performance with a maximum responsivity of 215 mA W^-1, an external quantum efficiency of 42.2%, specific detectivity of 1.05 × 10¹⁰ Jones, and response time of 8.6/4.2 ms under 635 nm illumination, respectively. In contrast, benefiting from the stronger in-plane anisotropic structure of thinner SnS component, the device delivers a large photocurrent anisotropic ratio of 4.6 under 635 nm illumination in a zigzag manner. Above all, our work provides a new design scheme for multifunctional optoelectronic applications based on thickness-dependent 2D vdWs heterostructures.