A power-free, filter-free and high-performance narrowband ZnO/BaTiO3/GaN heterojunction-based ultraviolet photodetector obtained by synergetic plasmonic and ferroelectric effects†

Narrowband ultraviolet photodetectors play a critical role in missile detection, flame monitoring, communication and other fields. Most commercial narrowband photodetectors, which are currently obtained by combining bandpass filters, face challenges including bandwidth limitations, additional optical losses, lower photoelectric conversion efficiency, and others. Herein, we present a filter-free, self-powered narrowband ultraviolet photodetector based on a heterojunction containing Pt nanoparticle-modified ZnO microwire via Ga-incorporation (PtNPs@ZnO:Ga MW), BaTiO₃ nanocrystal layer and p-GaN substrate. The PtNPs@ZnO:Ga/BaTiO₃/GaN heterojunction detector exhibits superior performance, exhibiting a remarkable responsivity of 265.9 mA W⁻¹, a specific detectivity of 1.1 × 10¹¹ Jones, a large on/off ratio of 4.5 × 10⁶, and a fast response speed of 5.3 μs/5.6 μs under 355 nm illumination at zero bias. Notably, the detector demonstrates a narrowband photoresponse with a bandwidth of about 4 nm, making it highly competitive in its class. The ultra-narrow bandwidth resulted from the self-polarization field induced by the interfaced BaTiO₃ nanolayer, which facilitates the exciton ionization process in the GaN layer. Besides, the combination of surface-coated PtNPs and the BaTiO₃ nanolayer enables the optimization and enhancement of built-in electric fields at the ZnO:Ga/GaN interface, thus demonstrating the feasibility of achieving high-performance ultra-narrow bandwidth photodetection in ultraviolet wavelengths. This work provides valuable insights and methodologies for the development of ultra-narrow bandwidth photodetection devices.