High Responsivity of Zero-Power-Consumption Ultraviolet Photodetector Using 2D-MoS₂/i-GaN Vertical Heterojunction

The wide bandgap semiconductor GaN has proven to be an excellent candidate for high-performance ultraviolet (UV) photodetectors owing to the direct bandgap, long lifetime, outstanding radiation hardness, and high thermal and chemical stability. To ultimately reduce the power consumption, self-powered operation is preferred. However, it is difficult to achieve a high responsivity when no external bias is applied for the reported self-powered Schottky, p-n junction, or hybrid GaN-based photodetectors. In this study, we report a UV photodetector with an ultrahigh photoresponsivity and fast response speed under zero-power consumption by integrating GaN with transition metal dichalcogenides (TMDs) MoS2 nanosheets through one-step hydrothermal and substrate compatible drop-casting method. Detailed characterization confirmed the formation of a 2D-MoS2/i-GaN vertical heterojunction with a few layers of hexagonal MoS2 nanosheets on a high-crystalline-quality GaN film. The photoresponsivity as high as 610 A/W and external quantum efficiency exceeding 2000% were achieved at the wavelength of 370 nm under zero external bias without sacrificing the response speed (similar to ms). The specific detectivity was estimated to be 1.22 x 10(14) Jones, and the UV/visible discrimination ratio was more than 2 orders of magnitude. The excellent performance of the 2D-MoS2/GaN-based vertical heterojunction UV photodetector could be attributed to the optimized heterointerface and the effective separation and transfer of photogenerated electron-hole pairs by the strong built-in electric field formed from the band alignment of the type-II heterojunction. This photodetector, with superior photoresponsivity at zero-power consumption, is promising for practical applications in areas such as sensing, imaging, and communication.