Gate-tunable polarization-sensitive photodetection based on in-plane anisotropic GeS single-crystal films

Abstract

Group IV–VI monochalcogenides have attracted considerable interest for polarization-sensitive photodetection due to their pronounced chemical stability and photoelectric anisotropy. However, scaling high-quality single-crystalline films over large areas remains challenging, limiting the active device area and ultimately the performance metrics of linear-polarization photodetectors. Furthermore, the origin and gate-tunability of valley-selective photoresponses in these materials are not fully understood. Herein, sub-centimeter-scale single-crystal GeS films with high lattice uniformity are successfully synthesized. Photodetectors based on these films exhibit strong wavelength-dependent linear dichroism, reaching a maximum polarization ratio of 2.7 at 670 nm. Significantly, a photoinduced bilateral Schottky-barrier lowering effect is identified, which provides an internal photo-gain, leading to the higher responsivity of 17.37 mA/W and detectivity of 2.77 × 1010 Jones at 405 nm. A gate voltage-modulated rotation of the polarization-sensitive photocurrent axis is observed, revealing a complex interplay between intrinsic anisotropy and external-field effects. Theoretical analysis indicates that the intrinsic dichroism originates from two distinct in-plane polarized valleys, while the gate-induced angular rotation is primarily driven by an anisotropic Pauli-blocking mechanism. These findings not only demonstrate a viable route for wafer-scale preparation of single-crystal GeS films but also provide fundamental insights into the electric modulation of linear dichroism, advancing the development of high-performance polarized photonic devices.