Ultrabroadband SnBi ₂ Te ₄ Photodetectors From Visible to Terahertz

ABSTRACT 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. SnBi 2 Te 4 , 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 SnBi 2 Te 4 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 (R i ) of the SnBi 2 Te 4 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 SnBi 2 Te 4 for ultrabroadband room‐temperature photodetection.