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

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.