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

Xinghan Cai, Andrei B. Sushkov, Ryan J. Suess, Mohammad M. Jadidi, Greg S. Jenkins, Luke O. Nyakiti, Rachael L. Myers-Ward, Jun Yan, D. Kurt Gaskill, Thomas E. Murphy, H. Dennis Drew,Michael S. Fuhrer

(Submitted on 14 May 2013 (v1), last revised 7 Nov 2013 (this version, v2))

http://arxiv.org/abs/1305.3297

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/Hz1/2, competitive with the best room-temperature THz detectors, while time-resolved measurements indicate our graphene detector is eight to nine 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.