ReS₂ Nanosheet/WS₂ Nanosheet/p-GaN Substrate Dual Junction Photodetectors

The broad application of ultraviolet (UV) photodetectors in civil, astronomical, and military fields has sparked significant research interest. Recently, two-dimensional layered transition metal dichalcogenides have emerged as an ideal platform for developing high-performance and versatile photodetectors due to their abundant intriguing optoelectronic properties. Here, we constructed a photodetector utilizing dual heterojunctions based on rhenium disulfide (ReS2) nanosheet/tungsten disulfide (WS2) nanosheet/p-type gallium nitride (p-GaN) substrate, which incorporate dual built-in electric fields. The built-in electric field at the WS2–p-GaN interface accelerates the separation of photogenerated electrons, enabling a fast photoresponse. Simultaneously, the built-in electric field at the ReS2–WS2 interface not only suppresses dark current but also confines photoexcited holes within the ReS2 layer, ultimately extending the lifetime of photocarriers. Consequently, a photogating effect with high photoconductive gain is achieved. Exploiting these advantages, the ReS2/WS2/p-GaN device exhibits a high responsivity of 3.78 A/W, an outstanding detectivity of 2.1 × 1012 Jones, and a fast rise/decay time of 259/374 μs under 365 nm light with a power density of 0.069 mW/cm2. Furthermore, the device demonstrates its potential for high-resolution UV imaging by functioning as a single pixel, showcasing its capabilities for advanced UV detection and imaging applications.