Key Factors in Achieving High Responsivity for Graphene-Based Terahertz Detection

Terahertz (THz) radiation is highly promising for various applications, from industrial inspections to medical diagnoses. Given the typically ultralow-level power of generated THz radiation, the achievement of high responsivity in THz detection stands as a critical imperative for its applications. Graphene-based detectors have become an attractive choice for THz detection due to the graphene unique 2D material structure, allowing a broad absorption spectrum and ultrafast response. Various plasmonic antenna arrays are also employed to couple with graphene, compensating for its modest optical absorption. However, the configuration of the plasmonic antenna arrays plays a crucial role in THz detection as it determines the graphene physical mechanisms of photodetection, directly impacting the final responsivity. Here, the key factors for achieving high responsivity are investigated and it is presented that reducing the gap size of the plasmonic antenna arrays to the nanoscale and implementing a series-connection configuration can result in a remarkable increase in responsivity, often by several orders of magnitude. Importantly, this approach effectively prevents short circuits and minimizes dark current, further enhancing the overall performance of the detection system.