Self-powered UV-NIR broadband photodetector based on 2d-bi₂Te₃/3d-GaN heterojunction for image sensing

Self-powered broadband photodetectors are critical for energy-efficient optoelectronics in the Internet of Things, environmental sensing, and wearable imaging, yet achieving broadband response with high specific detectivity in a device through a scalable fabrication method remains a major challenge. In this work, we report a Bi₂Te₃/GaN heterojunctionphotodetector that integrates narrow- and wide-bandgap semiconductors to realize self-powered operation from ultraviolet to near infrared region. The Bi₂Te₃/GaN heterostructure is fabricated by depositing a homogeneous Bi₂Te₃ film with high crystallinity on a GaN substrate through the electron beam evaporation method followed by a post-annealing. Without any external bias, the photodetector exhibits a broadband specific detectivity above 10⁹ Jones and a fast response lower than 100 m s in the 367-850 nm spectral range, attributed to efficient photogenerated carrier separation across the heterojunctiondue to the built-in electric field at the interface. Under 367 nm light irradiation, the device achieves a responsivity of 80.39 mA/W and a specific detectivity of 2.01 × 10¹² Jones. The device also demonstrates excellent cycling durability, maintaining stable photoresponse over 100 cycles at 638 nm illumination, and supports high-resolution and multi-wavelength imaging. This work provides a cost-effective, scalable strategy for constructing Bi₂Te₃/GaN heterojunctions and highlights the potential of Bi₂Te₃-based detectors for next-generation self-powered broadband photodetection technologies.