Hydrogen‐Assisted Synthesis of Large‐Size 2D Bismuth Telluride Flakes for Broadband Photodetection up to 2 µm

Abstract Broadband photodetection including optical communication wavelength band is of great significance because of the great potential for various civilian and military applications. Topological insulators with unique surface electronic states have attracted more and more attention in broadband photodetection. Among them, due to its suitable band gap (0.16–1.36 eV), ultra‐high mobility, and excellent air stability, 2D bismuth telluride (Bi 2 Te 3 ) is regarded as a promising candidate. However, the growth of large‐size Bi 2 Te 3 is challenging because of the poor chemical reactivity of tellurium (Te) element. Here, large‐scale (240 µm, ten times larger than the current record) Bi 2 Te 3 flakes with controllable thickness (one to few layers) are successfully synthesized by H 2 ‐assisted chemical vapor deposition. Thanks to the strong reducibility and the passivation on the substrate of H 2 , the growth rate is as high as 48 µm min −1 , which is ten times faster than that reported. Moreover, the Bi 2 Te 3 ‐photodetector exhibits broadband detection (520–2000 nm), high responsivity of 252 A W −1 , excellent detectivity of 5.1 × 10 11 cm Hz 1/2 W −1 , and fast response time (τ rise /τ decay ≈ 41/38 ms), implying potential applications in broadband optoelectronics. More importantly, this work may pave a way for the rapid growth of other novel large‐scale 2D materials.