2D In2S0.15Se2.85: A ternary alloy with strong in-plane anisotropy for polarization-sensitive optoelectronics

Two-dimensional III–VI semiconductors are promising for polarization-sensitive optoelectronics but are limited by weak intrinsic anisotropy (photocurrent ratio ∼2) and fixed bandgaps. Here, we report the synthesis of 2D In2S0.15Se2.85 ternary alloy nanoplates via atmospheric pressure chemical vapor deposition. Sulfur alloying widens the optical bandgap from 1.39 to 1.73 eV while preserving the non-centrosymmetric structure, enabling bandgap engineering. The alloy exhibits pronounced in-plane optoelectronic anisotropy, with conductivity and mobility ratios of 4.15 and 3.29, which amplifies the photocurrent polarization ratio to 3.6 at 405 nm and 3.5 at 635 nm. The fabricated photodetector achieves a high responsivity of 1.33 A/W and a specific detectivity of 8.55 × 1012 Jones, placing it among the top-performing anisotropic 2D photodetectors. Leveraging these metrics, we demonstrate high-contrast polarization-resolved imaging. This work establishes 2D In2S0.15Se2.85 as a versatile platform for next-generation polarization-sensitive optoelectronics.