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

Abstract

Broadband photodetection including midwave infrared (MWIR) is crucial in space science and technology. Topological insulators Bi 2 Se 3 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 Bi 2 Se 3 /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 Bi 2 Se 3 /BP photodetector from visible to mid-infrared (520–4250 nm) with the fastest response time reaching 92 μs (τ rising ) and 84 μs (τ falling ), 3 orders of magnitude faster than Bi 2 Se 3 detector. The responsivity ( R ) and detectivity ( D *) can reach up to 1.13 A W -1 and 7.8 × 10 9 cm Hz 1/2 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.