▎ 摘　　要

Graphene-based photodetectors suffer from low light absorption of about 2.3%. In order to increase the absorption and responsivity, we design a periodic array of metallic nanostructures placed on the graphene absorbing layer to interact and resonate with the incident beam and hence increase the optical field, leading to enhanced absorption. This metallic photonic crystal is designed to exhibit two resonance frequencies in the mid- and long-infrared range to enable two-color detection of the photodetector. The optical absorption parameters of the detector are obtained using finite-difference time-domain (FDTD) simulations, and the effect of gate and drain voltages is studied using analytical models. The results show that the use of gold photonic crystals increases the absorption and responsivity. The response in the range of 3-5 mu m for the graphene-based photodetectors using gold photonic crystals is in the range of 29 A/W, and the responsivity of graphene-based photodetectors without photonic crystals is 0.95 A/W, about 29 times higher than a conventional detector. The results also show that by using this structure, the long-IR response of the detector is enhanced about sixfold. In comparison to previous similar works, greater enhancement is achieved by implementing this structure. The peak responsivity in the mid-IR is about 29 A/W, which is enhanced in comparison to the highest value reported for this type of detector of about 27.4 A/W.