Van der Waals Epitaxy of Bi2Te2Se/Bi2O2Se Vertical Heterojunction for High Performance Photodetector

Abstract Bismuth oxyselenide (Bi 2 O 2 Se) has emerged as a promising candidate for electronic and optoelectronic applications due to its outstanding electron mobility and ambient stability. However, high dark current and relatively slow photoresponse that originate from high charge carrier concentration as well as bolometric effect in Bi 2 O 2 Se inhibit further improvement of Bi 2 O 2 Se based photodetectors. Here, a one‐step van der Waals (vdW) epitaxy synthesis of Bi 2 Te 2 Se/Bi 2 O 2 Se vertical heterojunction with type‐II band alignment and high‐quality interface is demonstrated. The crystal quality and uniformity of the heterojunction are supported by Raman, transmission electron microscopy and energy dispersive spectroscopy results. A photodetector based on Bi 2 Te 2 Se/Bi 2 O 2 Se heterojunction demonstrates steady photoresponse over a large wavelength range (532–1456 nm), with a high specific responsivity of 2.21 × 10 3 A W –1 at 532 nm and fast response speed of 50 ms. Moreover, field effect regulation allows for further improvement of the photoresponse performance of the heterojunction field effect transistor device, where the responsivity can be increased to 3.34 × 10 3 A W –1 with a 60 V gate voltage. Overall, the one‐step vdW epitaxy process is a promising and convenient route towards constructing high quality Bi 2 O 2 Se based heterojunction for improving its photodetection performance.