Design and performance simulation of microcavity enhanced bilayer graphene infrared photodetector

Photodetectors based on bilayer graphene have raised great interest for its application in infrared and terahertz detection, because bilayer graphene performs well in optical and electrical area. However, weak light absorption of bilayer graphene limits the property of bilayer graphene photodetector. In this paper a design of microcavity enhanced infrared photodetector based on Bernal stacking bilayer graphene is presented. Quantum efficiency and responsivity of detector can be valid improved by confining light in the cavity. Theoretical analysis shows that microcavity length and reflectivity of reflectors are the key factors to influence the performance. When the microcavity length matches the operating wavelength, under the standing wave effect, the quantum efficiency can reach the maximum, while reflectivity becomes the key factor. To obtain a higher and more detailed reflectivity of reflectors, distributed bragger reflectors (DBRs) are chosen as reflectors of microcavity. Reflectivity is determined through the analysis of electromagnetic field distribution of membrane. The reflectivity of reflectors is calculated by transfer matrix. AlAs/Al0.1Ga0.9As and TiO2/SiO2 membranes are chosen as constituents of reflectors. The structure is confirmed through optimization, and the result is presented below: The microcavity length is 467.4 nm, 13/10 pairs of membranes constructs the top/bottom reflector and the bilayer graphene is located in the middle of microcavity. At a nominal operating wavelength of 1.55 mu m, a widely used wavelength in laser range finder, the quantum efficiency can reach 99.33% and the responsivity can reach 1.24 A/W. The method provides a possible approach to fabricate high quantum efficiency bilayer graphene photodetector.