A promising path towards creating these ultrafast diodes has been in the form of "geometric diodes". Graphene geometric diodes have been reported to rectify terahertz radiation. In April 2020, geometric diodes were reported in silicon nanowires. The wires were shown experimentally to rectify up to 40 GHz, but that was instrument limited, and theoretically may be able to rectify signals in the THz region as well.
