High zero-bias responsivity induced by photogating effect in asymmetric device structure

Graphene photodetectors based on photogating effect are promising due to the high photogain, but with the drawback of large dark current due to external bias. In this paper, we realized a graphene photodetector working at zero bias with high responsivity. By establishing asymmetric structure using CdS film on different part of graphene channel, the influence of asymmetric ratio on device performance were found to be opposite for external and zero bias. Without external bias, the responsivity can reach 0.26 A/W under visible light, resulting in a quantum efficiency of 51.5%, which is much larger than other zero-bias graphene photodetectors based on photothermoelectric effect. Furthermore, based on the asymmetric structure, infrared photoresponse beyond the CdS cut-off wavelength was observed at 980 nm wavelength at low temperature. This work provides a feasible scheme for the low energy consumption work of photodetectors with low dimensional materials.