Cross‐Substitution Promoted Ultrawide Bandgap up to 4.5 eV in a 2D Semiconductor: Gallium Thiophosphate

Abstract Exploring 2D ultrawide bandgap semiconductors (UWBSs) will be conductive to the development of next‐generation nanodevices, such as deep‐ultraviolet photodetectors, single‐photon emitters, and high‐power flexible electronic devices. However, a gap still remains between the theoretical prediction of novel 2D UWBSs and the experimental realization of the corresponding materials. The cross‐substitution process is an effective way to construct novel semiconductors with the favorable parent characteristics (e.g., structure) and the better physicochemical properties (e.g., bandgap). Herein, a simple case is offered for rational design and syntheses of 2D UWBS GaPS₄ by employing state‐of‐the‐art GeS₂ as a similar structural model. Benefiting from the cosubstitution of Ge with lighter Ga and P, the GaPS₄ crystals exhibit sharply enlarged optical bandgaps (few‐layer: 3.94 eV and monolayer: 4.50 eV) and superior detection performances with high responsivity (4.89 A W⁻¹), high detectivity (1.98 × 10¹² Jones), and high quantum efficiency (2.39 × 10³%) in the solar‐blind ultraviolet region. Moreover, the GaPS₄‐based photodetector exhibits polarization‐sensitive photoresponse with a linear dichroic ratio of 1.85 at 254 nm, benefitting from its in‐plane structural anisotropy. These results provide a pathway for the discovery and fabrication of 2D UWBS anisotropic materials, which become promising candidates for future solar‐blind ultraviolet and polarization‐sensitive sensors.