Submillimeter 2D Bi2Se3 Flakes toward High‐Performance Infrared Photodetection at Optical Communication Wavelength

Abstract Infrared detection at optical communication wavelength is of great significance because of their diverse commercial and military communication applications. The layered Bi 2 Se 3 with a narrow band gap of 0.3 eV is regarded as a promising candidate toward high‐performance terahertz to infrared applications. However, the controllable synthesis of large‐size ultrathin Bi 2 Se 3 flakes remains a challenge owing to complex nucleation process and infrared telecommunication photodetectors based on Bi 2 Se 3 flakes are rarely reported. Here, large size (submillimeter: 0.2–0.4 mm in lateral dimensions) and ultrathin (thickness: 3 nm to few nanometers) 2D Bi 2 Se 3 flakes with high crystal quality are obtained by suppressing the nucleation density. More importantly, back‐gate field‐effect transistor based on Bi 2 Se 3 flake exhibits an ultrahigh on/off current ratio of 10 6 and competitive mobility of 39.4 cm 2 V −1 s −1 . Moreover, excellent on/off ratio of 972.5, responsivity of 23.8 A W −1 , and external quantum efficiency of 2035% are obtained from Bi 2 Se 3 ‐based photodetector at 1456 nm in the E‐band of the telecommunication range. With controlled morphology and excellent photoresponse performance, the Bi 2 Se 3 photodetector shows great potential in the optoelectronic field including communications, military, and remote sensing.