Controllable Coupling Effects Enhance the Performance of Ionic-Polymer-Gated Graphene Photodetectors

Interface coupling of graphene/semiconductor heterostructures has been studied extensively for applications such as photodiodes, solar cells, and photodetectors as the demand for efficiency and performance increases. Here, a method is proposed to enhance the photogain of graphene/silicon photodetectors. The method is to manipulate the interface coupling of graphene/silicon by optimizing the voltage of ionic polymer gate. The high responsivity from the visible to infrared regime (1.1 × 104 A/W at 635 nm and 15 A/W at 1550 nm) is obtained by using the method. The enhancement magnitude is as high as about 5–8 times relative to the devices in literature not using the method. The mechanism is studied and attributed to the photogating effect through analyzing carrier transport of graphene and potential distribution in the heterojunction region under top-gate manipulation. Furthermore, the double-gate enhancement method is proposed based on the graphene/silicon-on-insulator structure, and the responsivity of a new device can be improved by 500 times as compared with the original device. This work has reference significance for the interface optimization of a hybrid structure photodetector based on graphene/semiconductor.