Highly Enhanced SWIR Image Sensors Based on Ge_1–<i>x</i>Sn_<i>x</i>–Graphene Heterostructure Photodetector

Ge1–xSnx with a tunable bandgap that covers full shortwave infrared (SWIR) from 1 to 2.6 μm presents a new paradigm for silicon-based SWIR photodetection. However, low absorption and high surface recombination remain to be large limitations for realization of high performance photodetector. This work demonstrates GeSn–graphene heterostructure photodetectors with high responsivity, photoconductive gain, and detectivity can effectively lessen the burdens. Compared with the pure GeSn photodetector, the introduction of graphene not only effectively solves the problem of serious surface states of the GeSn active layer, but achieves large enhancements in both photocurrent and response speed, even under a relatively weak illumination, which indicates photogenerated carriers can be separated and transported in higher efficiency. At the same time, there is no recession in performance after a 4 month exposure in ambient environment. In addition, the heterostructure is integrated into a 20 × 20 pixel detector array with a size of 440 × 440 μm2 and an image of letter “E” is clearly obtained according to a mask measurement method. The compatibility with CMOS technique offers such photodetector new opportunities for application in SWIR optical communication and imaging, remote sensing, and biomedical.