Abstract-Sensitive Room-Temperature Terahertz Detection via Photothermoelectric Effect in Graphene

http://arxiv.org/abs/1305.3297
 Xinghan Cai, Andrei B. Sushkov, Ryan J. Suess, Greg S. Jenkins, Jun Yan, Thomas E. Murphy, H. Dennis Drew, Michael S. Fuhrer

Terahertz (THz) radiation has uses from security to medicine, however sensitive room-temperature detection of THz is notoriously difficult. The hot-electron photothermoelectric effect in graphene is a promising solution: photoexcited carriers rapidly thermalize due to strong electron-electron interactions, but lose energy to the lattice more slowly. The electron temperature gradient drives electron diffusion, and asymmetry due to local gating or dissimilar contact metals produces a net current via the thermoelectric effect. Here we demonstrate a graphene thermoelectric THz photodetector with sensitivity exceeding 100 V/W at room temperature and noise equivalent power (NEP) less than 100 pW/Hz^1/2, competitive with the best room-temperature THz detectors, while time-resolved measurements on similar devices indicate our graphene detector is more than seven orders of magnitude faster. A simple model of the response, including contact asymmetries (resistance, work function and Fermi-energy pinning) reproduces the qualitative features of the data, and indicates that orders-of-magnitude sensitivity improvements are possible.