Ultrabroadband SnBi2Te4 Photodetectors From Visible to Terahertz.

Ultrabroadband photodetectors (UB-PDs) are seeing burgeoning deployment across a lot of technologies, including artificial intelligence, healthcare, optical communications, and biomedical imaging, which prompts urgent demands for high-performance UB-PDs. However, the existing photodetectors usually suffer from limitations of narrow operational bandwidth and low sensitivity at room temperature. SnBi2Te4, a novel topological insulator intercalation material, exhibits a narrow bandgap, unique surface-state conductive transport properties, and a tunable band gap, making it an ideal candidate for room-temperature ultrabroadband photodetection. In this study, we synthesize high-quality layered SnBi2Te4 crystals using the Chemical Vapor Transport (CVT) method. The fabricated detector achieves high-performance broadband detection from visible to terahertz (THz) light through synergistic mechanisms of the conventional photoelectric effect and the electromagnetic-induced well effect. In the visible-infrared region, the photodetector shows a noise equivalent power of 8.5 pW·Hz-1/2 with the response time of 70 µs and responsivities of 19.4 A·W-1 at 980 nm and 13.9 A·W-1 at 635 nm, respectively. Additionally, the current responsivity (Ri) of the SnBi2Te4 photodetector is 0.117 A·W-1 at the mid-wave infrared (MWIR, 3 µm) band and 0.063 A·W-1 at the long-wave infrared (LWIR, 10.6 µm) band. In the terahertz region, this detector achieves sensitive detection across the 0.02-0.519 THz spectral band, exhibiting an ultrafast response time of 1.83 µs. Finally, the excellent performance of the detectors is demonstrated by high-resolution THz transmission imaging experiments at room temperature. Our study confirms the significant advantages of SnBi2Te4 for ultrabroadband room-temperature photodetection.