Mid‐Wave Infrared Polarization‐Independent Graphene Photoconductor with Integrated Plasmonic Nanoantennas Operating at Room Temperature

Abstract Graphene photodetectors operating in the mid‐wave infrared (MWIR) face challenges that include the optical absorption of monolayer graphene being intrinsically low and the carrier lifetime in graphene being very short. Previous reports of graphene photoconductors in the MWIR have sought to overcome these challenges using approaches that include the integration of plasmonic nanoantennas and/or engineered electrodes. However, this has led to the photoresponse of these detectors being strongly polarization dependent. Here, a graphene photoconductor is reported that achieves polarization‐independent and fast response simultaneously via the integration of plasmonic nanoantennas that are termed Jerusalem‐cross antennas (JC‐antennas). Compared to previous works, the JC‐antennas concentrate the incident light onto graphene more efficiently with enhanced polarization‐independent optical absorption. MWIR detection is demonstrated at both room temperature and cryogenic temperatures, with measured responsivity of 14.5 V W⁻¹ (room temperature) and 4400 V W⁻¹ (78 K). Due to the carrier collection by the JC‐antennas and gapless band structure of graphene, the detector also shows significant and broadband photoresponse that extends to visible and near‐infrared wavelengths. The detector shows fast temporal response with a measured rise time of 3 ns, which would be more than sufficient for many practical applications (e.g., imaging).