Electrostatically Controlled Graphene Thermocouple

Graphene has a broad-band optical absorption ranging from the visible ($\lambda $\textless 532 nm) all the way to the far-infrared ($\lambda $\textgreater 10$\mu$m). Additionally, graphene's optical phonon energy and electrostatically tunable Fermi energy are in the mid-infrared energy range. Together, determining these properties could enable a new generation of carbon-based infrared photodetectors. Electrostatically gated p-n junctions have demonstrated photocurrents in near-IR measurements (850nm), generated primarily through photo-thermoelectric effects. By fabricating electrostatically controlled p-n junctions using chemically vapor grown graphene, we determine the photoresponse mechanism to be primarily thermoelectric in nature at mid-infrared wavelengths and strongly influenced by substrate interactions.