▎ 摘　　要

We present the model of an ultrasensitive mid-infrared (mid-IR) photodetector consisting of a hybrid heterostructure made of nanopatterned graphene (NPG) and vanadium dioxide (VO2) which exhibits a large responsivity of R similar to 10(5) V/W, a detectivity exceeding D* similar to 1010 Jones, and a sensitivity in terms of noise-equivalent power NEP similar to 10 fW/root Hz close to room temperature by taking advantage of the phase change of a thin VO2 film. Our proposed photodetector can reach an absorption of nearly 100% in monolayer graphene because of localized surface plasmons (LSPs) around the patterned circular holes. The geometry of the nanopattern and an electrostatic gate potential can be used to tune the absorption peak in the mid-IR regime between 3 and 12 mu m. After the photon absorption by the LSPs in the NPG sheet, the phase change of VO2 from insulating to metallic phase is triggered, resulting in a current through the VO2 sheet due to the applied bias voltage V-b. The response time is about 1 ms, shorter than the detection times of current VO2 bolometers. With use of a gradient thickness of the VO2 layer, a linear dependence between input power P-inc of the incident light and the photocurrent I-ph is achieved. Our envisioned mid-IR photodetector reaches detectivities of cryogenically cooled HgCdTe photodetectors and sensitivities larger than VO2 microbolometers while operating close to room temperature.