High photocurrent and quantum efficiency of graphene photodetector using layer-by-layer stack structure and trap assistance

Two approaches, graphene stack (GS) structure assembled by layer-by-layer (LBL) transfer and trap assistant technique for single-layer graphene (SLG), are applied to field-effect transistors (FETs) for photodetection. In LBL-GS-FET, about 3.6 times increased photocurrent (PC) together with increased internal/external quantum efficiency (IQE/EQE) is obtained compared to the conventional SLG-FET, owing to an improvement of both electrical transport and optical absorption. In trap-assisted SLG-FET, the PC over 12% compared to the dark current with the superior photo-responsivity (S) of 2.8 mA/W and the IQE/EQE of 23.0%/ 0.5% is obtained, due to the different response of trapping effect in dark and illumination environments.