Ultrafast sensitive broadband imaging photodetection based on vertically stacked structured GaN/Bi₂O₂Te/Bi₂Te₃ p-n heterojunctions

Bismuth oxychalcogenides (Bi₂O₂X; X = S, Se, Te) hold promise as novel candidates for room temperature ultrasensitive optoelectronic devices. However, the relaxation of devices caused by the thermoelectric effect severely limits their application in ultrafast photodetectors. In this study, a vertical p-GaN/Bi₂O₂Te/Bi₂Te₃ heterojunction is fabricated using a simplified chemical vapor deposition technique, successfully achieving modulation of the response performance of the heterojunction device with the assistance of a weak electric field. Under 254 nm irradiation with a bias voltage of −0.1 V, the device exhibits a responsivity of 671.9 mA/W and a specific detectivity of 9.099 × 10¹⁰ Jones, as well as a rise time of 1.83 ms and a decay time of 1.76 ms. Particularly noteworthy is the ultrafast response exhibited by the device in both the UV and NIR bands, with τ_rise and τ_decay of 74.2 μs and 162.0 μs under 405 nm irradiation, and 126 μs and 130 μs under 980 nm irradiation, respectively. Furthermore, the p-GaN/Bi₂O₂Te/Bi₂Te₃ device exhibits excellent stability and outstanding imaging capability under broadband irradiation. This significant research lays the groundwork for future applications and the development of novel broadband multifunctional photodetectors.