Topological Insulator Bi2Se3 Heterojunction with a Low Dark Current for Midwave Infrared Photodetection

Broadband photodetection including midwave infrared (MWIR) is crucial in space science and technology. Topological insulators Bi2Se3 have exhibited excellent performance in infrared. However, the large dark current caused by topological surface states impedes further photodetection capability enhancement. Here, we designed and integrated the Bi2Se3/BP van der Waals p-n heterojunction to suppress dark current. The built-in electric field and clean, sharp interface at heterojunctions drive excellent photoresponse of the Bi2Se3/BP photodetector from visible to mid-infrared (520–4250 nm) with the fastest response time reaching 92 μs (τrising) and 84 μs (τfalling), 3 orders of magnitude faster than Bi2Se3 detector. The responsivity (R) and detectivity (D*) can reach up to 1.13 A W-1 and 7.8 × 109 cm Hz1/2 W-1, respectively, at 2 μm under 0 bias. Due to the asymmetric lattice structure of BP, the heterojunction device displays outstanding polarization-resolved photoelectric response, with a polarization ratio of up to 20.1 at 2 μm. Moreover, the device exhibits a significant blackbody response and excellent imaging capabilities. This work may pave a way for designing high-performance midwave infrared photodetectors.