High Frequency Characteristics of Graphene Geometric Diodes

Geometric diodes have the potential to provide ultra-fast rectification [1] , which can be used in rectennas for high-efficiency conversion of infrared signals into DC electrical power. We present for the first time simulations of the high frequency characteristics of these devices, to supplement previous measurements at 28 THz. The operating principle of the geometric diode is shown in Fig. 1 . Charge carriers are funneled in one direction more easily than the other, giving rise to diode behavior. To facilitate the geometric effect, ballistic transport is needed, which requires the mean-free path length of charge carriers to be on the order of, or larger than, critical device dimensions [2] . To be fabricable, these dimensions must be on the order of at least tens of nanometers which makes graphene, with room- temperature mean-free path lengths approaching 1 μm [3] , an attractive material choice. In this size regime, the possibility of high frequency operation is possible as charge transport is not limited by diffusive scattering. We developed a Monte Carlo simulator to compute high frequency current-voltage characteristics for a graphene geometric diode. We find that the diode behavior extends into the terahertz range with a cutoff falling near graphene’s damping parameter as predicted by Drude conductivity.