Nano-Interface Charge Transfer in Ga₂O₃@(Co, Ni)S₂ Heterojunction Ultraviolet Photodetectors

Constructing nanoheterojunction is a crucial approach to achieving self-powered ultraviolet photodetectors based on Ga2O3. Two-dimensional modified NiS2 nanosheets are excellent candidates for fabricating nanoheterojunctions due to their high electrical conductivity for efficient charge transport, large surface area for enhanced light absorption, and exceptional chemical and thermal stability for reliable long-term UV detection. Herein, two-dimensional bimetallic (Co, Ni)S2 nanosheets are proposed using a two-step hydrothermal synthesis method. Subsequently, a 3D/2D Ga2O3@(Co, Ni)S2 heterojunction is constructed by depositing (Co, Ni)S2 nanosheets onto the Ga2O3 nanowire network. Ga2O3@(Co, Ni)S2 heterojunction photodetector achieves a self-driven responsivity of 36.56 mA W1– under 254 nm illumination, which is higher than the heterojunction photodetector based on Ga2O3 and monometallic NiS2 photodetector. Under 10 V bias, Ga2O3@(Co, Ni)S2 heterojunction photodetector exhibits a high responsivity, detectivity, and external quantum efficiency of 1.51 A W1–, 7.68 × 1012 Jones, and 738.27%, which are 174.11, 8.95, and 174.11 times greater than those of pure Ga2O3 photodetector. The Ga2O3@(Co, Ni)S2 photodetector also displays a faster response speed than that of the pure Ga2O3 photodetector. Calculated charge density differences show that improved performances are attributed to the advanced band alignment and interface charge transfer by forming the type I heterostructure between Ga2O3 and (Co, Ni)S2. The established built-in electric field and lower Schottky barrier facilitate the effective transfer of photoelectrons at the nanointerface. Furthermore, the enhanced light absorption capacity and elevated conductivity of (Co, Ni)S2 contribute to the improved photoelectric conversion capability. This research highlights that 2D bimetallic sulfide nanomaterials play a significant role in developing Ga2O3-based self-driven photodetectors.