Broadband Bi₂O₂Se Photodetectors from Infrared to Terahertz

2D Bi₂O₂Se has shown great potential in photodetector from visible to infrared (IR) owing to its high mobility, ambient stability, and layer-tunable bandgaps. However, for the terahertz (THz) band with longer wavelength and richer spectral information, there are few reports on the research of THz detection based on 2D materials. Herein, an antenna-assisted Bi₂O₂Se photodetector is constructed to achieve broadband photodetection from IR to THz ranges driven by multi-mechanism of electromagnetic waves to electrical conversion. The good tradeoff between the bandgap and high mobility results in a broad spectral detection. In the IR region, the nonequilibrium carriers result from photo-induced electron-hole pairs in the Bi₂O₂Se body. While in the THz region, the carriers are caused by the injected electrons from the metal electrodes by the electromagnetic-induced well. The Bi₂O₂Se photodetector achieves a broadband responsivity of 58 A W^-1 at 1550 nm, 2.7 × 10⁴ V W^-1 at 0.17 THz, and 1.9 × 10⁸ V W^-1 at 0.029 THz, respectively. Surprisingly, an ultrafast response time of 476 ns and a quite low noise equivalent power of 0.2 pW Hz^−1/2 are acquired at room temperature. Our researches exhibit promising prospects of Bi₂O₂Se in broadband detection, THz imaging, and ultrafast sensing.