High Performance Room Temperature Rectenna IR Detectors Using Graphene Geometric Diodes

High performance rectenna detectors that operate at room temperature have been developed for the frequency range of terahertz to infrared (IR). We formed IR rectennas by coupling bowtie antennas to ultrafast diodes, called geometric diodes. Geometric diodes rely on geometric asymmetry and the long charge carrier mean-free path length of graphene to provide asymmetric current-voltage characteristics. The planar structure of the geometric diode provides the femtosecond RC time constant necessary for detection of IR frequencies. Fabricated IR rectennas using graphene geometric diodes have shown strong optical response to 28 THz CO$_{2}$ laser illumination at room temperature. The detectivity $({\rm D}^*)$ and the noise equivalent power (NEP) of the IR rectennas are calculated to be on the order of $10^{8}$ cm Hz$^{1/2}{\rm W}^{-1}$ and $10^{-9}$ W ${\rm Hz}^{-1/2}$, respectively. Simulations show that with some improvement room temperature rectennas using graphene geometric diodes are able to achieve an NEP value as low as $10^{-11}$ W ${\rm Hz}^{-1/2}$ .