Super-high responsivity and harsh environment-resistant ultraviolet photodetector enabled by Ta₂NiSe₅/GaN van der Waals heterojunction

Gallium nitride (GaN) has garnered significant research interest for ultraviolet (UV) photodetectors due to its direct bandgap, inherent UV absorption window, and high breakdown voltage. In this work, a new ternary chalcogenides Ta₂NiSe₅ with high mobility is successfully stacked with unintentionally-doped GaN to creat an integrated mixed-dimensional Ta₂NiSe₅/GaN (2D/3D) van der Waals heterojunction with a typical type-I band alignment. The resulting Ta₂NiSe₅/GaN heterojunction exhibits excellent UV detection performance, with a pronounced light on/off ratio of 10⁷ and a large responsivity of 1.22 × 10⁴ A W⁻¹. Moreover, it demonstrates an enhanced detectivity up to 1.3 × 10¹⁶ Jones under 365-nm light illumination at a bias of 4 V. The photodetector also exhibits a fast response speed of 1.22/3.16 ms. Remarkably, the device showcases exceptional stability, repeatability, and tolerance to harsh environmental conditions, including high temperature and acidic condition. Furthermore, leveraging the high responsivity, detectivity, and light on/off ratio of the photodetector, we successfully integrate this heterojunction device into UV optical communication, high-lighting its potential in information transmission.