▎ 摘　　要

Graphene-based photodetectors have drawn a large amount of interests owing to its wide spectral response, however, the high dark current greatly limits their applications. In this study, we develop an efficient graphene in-plane homogeneous p-n-p junction based infrared (IR) photodetector with greatly reduced dark current. The devices with p-n-p junctions exhibit excellent photoresponse to 1.0 similar to 4.0 mu m IR light illumination with ultra-low dark current at the order of similar to 10(-9) A in double p-n-p junctions and 10(-13) A in three p-n-p junctions based photodetector, which is three and seven orders of magnitude lower than pristine graphene phototransistors, respectively. The excellent IR photodetection capabilities could be attributed to the synergistic effects of in-plane photovoltaic effects as well as the photogating effects induced carrier injection from the silicon substrate. Our results suggest intriguing potential of graphene in-plane p-n-p junctions for applications in high-performance IR photodetectors.