Low‐Symmetry Van der Waals Dielectric GaInS₃ Triggered 2D MoS₂ Giant Anisotropy via Symmetry Engineering

Low-symmetry structures in van der Waals materials have facilitated the advancement of anisotropic electronic and optoelectronic devices. However, the intrinsic low symmetry structure exhibits a small adjustable anisotropy ratio (1-10), which hinders its further assembly and processing into high-performance devices. Here, a novel 2D anisotropic dielectric, GaInS₃ (GIS), which induces isotropic MoS₂ to exhibit significant anisotropic optical and electrical responses is demonstrated. With the excellent gate modulation ability of 2D GIS (dielectric constant k ∼12), MoS₂ field effect transistor (FET) shows an adjustable conductance ratio from isotropic to anisotropic under dual-gate modulation, up to 10⁶. Theoretical calculations indicate that anisotropy originates from lattice mismatch-induced charge density deformation at the interface. Moreover, the MoS₂/GIS photodetector demonstrates high responsivity (≈4750 A W^-1) and a large dichroic ratio (≈167). The anisotropic van der Waals dielectric GIS paves the way for the development of 2D transition metal dichalcogenides (TMDCs) in the fields of anisotropic photonics, electronics, and optoelectronics.