Ultrafast and broadband graphene photodetectors based on plasmonic nanoantennas

Abstract

We present an ultrafast and high responsivity graphene photodetector that operates over a broad bandwidth from visible to infrared regime. Use of plasmonic nanoantennas as photodetector contact electrodes provides a strong concentration of photo-generated carriers near the contact electrodes. As a result, a large number of the photocarriers drift to the photodetector contact electrodes despite the short carrier lifetime of graphene, providing high responsivity levels. The photodetector is also designed to offer high speed operation by minimizing capacitive parasitics. We demonstrate broadband photodetection from 800 nm to 20 μm with operation speeds exceeding 50 GHz and responsivity levels as high as 0.6 A/W at 800 nm and 11.5 A/W at 20 μm. These results are the first demonstration of high-responsivity photodetection with such a broad operation bandwidth and high speed, enabled by plasmonic nanoantennas.