Valley-Selective Linear-Polarization Photodetectors Based on the Photogating Heterostructure of SnS/Si

Low-symmetry two-dimensional group-IV monochalcogenides with in-plane anisotropy offer a promising platform for chip-integrated polarization-resolved photonic devices. However, the valley-selective anisotropic photocurrent dynamics in these materials remain to be further identified through angle-resolved transport studies. Moreover, several technical challenges must be overcome to achieve devices with higher figures of merit without compromising dichroic performance. Here, using as-grown monochalcogenide SnS flakes and a dry-transfer technique, we fabricated polarization-resolved SnS/Si photodetectors. Under 405 nm linearly polarized light illumination, the devices exhibit an intrinsic photocurrent response preferential along the zigzag direction, with a typical dichroic ratio of 1.28. This photoelectric dichroism is attributed primarily to the polarized photoexcitation of the two in-plane valleys in SnS, with the dominant photocurrent direction governed by the zigzag-polarized valley possessing the smallest bandgap. Importantly, owing to hole-trapping-induced photogating gain at the SnS/Si interface driven by the inverted band offsets, the fabricated photodetectors achieve a high responsivity of 4.54 A W^-1, a detectivity of 4.76 × 10¹⁰ Jones, and enhanced self-powered operation. This work provides fundamental transport evidence for the predicted valley-selective photocurrent-output mechanism in SnS flakes and offers a viable route toward multifunctional, silicon-compatible, polarization-sensitive photonic devices.