  Thermoelectric readout in a graphene THz radiation detector requires a p-n
junction across the graphene channel. Even without an intentional p-n junction,
two latent junctions can exist in the vicinity of the electrodes/antennas
through the proximity to metal. In a symmetrical structure, these junctions are
connected back-to-back and therefore counterbalance each other with regard to
rectification of the ac signal. Because of the Peltier effect, a small dc
current results in additional heating in one- and cooling in another p-n
junction, thereby breaking the symmetry. The p-n junctions then no longer
cancel, resulting in a greatly enhanced rectified signal. This allows to
simplify the design and effectively control the sensitivity of the
THz-radiation detectors.
