Dual-Enhanced Photodetectors Combining Graphene Plasmonic Nanoresonators With Germanium-on-Insulator Optical Cavities

Two-dimensional graphene (2-D graphene) has limited application potential in optoelectronics because of its low light absorptivity and gapless property. This work presents photodetectors with increased light absorption efficiency, which couple 3-D graphene with the optical cavity structure of germanium-on-insulator (GeOI). Multiple reflections are generated at the 3-D graphene/GeOI heterojunction due to the unique plasmonic nanoresonator and optical cavity structures. The photodetectors exhibit excellent responsivity ( ${R}\,{=}\,0.9\,{\times }\,10^{4}$ mAW ⁻¹ ) and specific detectivity ( ${D}^{\ast }\,{=}\, 3.96\,{\times }\,10^{10}$ cmHz $^{1/2}\text{W}$ ⁻¹ ) under 1550-nm illumination with fast response rates, excellent reproducibility, and long-term stability. The technique paves the way for creating novel high-performance graphene-based photodetectors with hybrid architectures.