Novel antenna-coupled terahertz photodetector with graphene nanoelectrodes

Antenna-coupled photomixers, serving as emitters and receivers of terahertz (THz) radiation, are the central active components of coherent optoelectronic THz systems. Here, we focus on the continuous-wave modality, which finds ample use for spectroscopy, sensing, and ranging and plays a major role in upcoming ultrahigh-frequency telecommunication applications. We demonstrate with planar receivers based on low-temperature-grown GaAs that the use of interdigital graphene electrodes instead of metal fingers enhances the responsivity by more than one order of magnitude. The increase in responsivity leads to a strongly enlarged dynamic range and doubles the frequency range covered in the detection process. We show by simulations that these improvements are a consequence of the transparency of the finger electrodes for visible/near-infrared laser radiation, which also activates the area under the fingers for the mixing process, not only their edges as in conventional devices with metal electrodes.