Interfacial Photogating Effect for Hybrid Graphene-Based Photodetectors

Ultrafast and high-sensitive photodetectors operating from the deep-ultraviolet to near-infrared region at room temperature are essential for many applications such as analytical chemistry, optical positioning, biomedical imaging, and remote sensing. Toward high-performance photodetectors, hybrid colloid quantum dots/graphene photodetectors based on the photogating mechanism have been intensively studied. An ultrahigh sensitivity has been obtained in the range from 105 to 109 A/W but the major challenge of these configurations is the slow operating speed on the millisecond to second time scale. Manipulating the transferring of carriers at the interface of semiconductor nanostructures and graphene is an essential key to optimize the interfacial photogating effect. Here, we grow an absorber layer directly on graphene by e-beam evaporation to obtain a fast photoresponse time of the detectors. Thus, the gap between the high responsivity and fast response time can be bridged. The photodetectors indicate a high photoresponsivity of ∼2.5 × 106 A/W at low incident intensity on the order of femto-watts, a specific detectivity of ∼8.5 × 1011 Jones, and a fast response process of ∼20 ns together with a slow component of ∼850 ns (response time of <1 μs) under a drain-to-source bias of 100 mV. The study has provided a method to obtain high-performance photodetectors based on graphene with high responsivity and fast response time.