Abstract

Generating electron-hole pair through photon absorption is routinely the photodetection process promoting widespread applications ranging from security to human life. Recently, exploiting terahertz (THz) photodetection technique receives unprecedented attention due to its great promising for noninvasive imaging, communication, etc^1,2. However, it is still lacking of efficient way for sensitive room-temperature detection due to the low photon energy. Gapless graphene is highly sought-after as a potential candidate for active material in photodetection across whole spectrum. Even though considerable amount of THz photons can be absorbed by graphene, the efficient photo-to-electric conversions are not well-developed. Among them, photodetection dominated by the plasma wave nonlinear-rectifying and photothermoelectric effects by exploiting specific device structure, chemical doping or dissimilar contacts are proposed^3-5. Beyond the conventional interband mechanism, we report biased photoconductive detector but otherwise homogeneous graphene-channel with sensitivity exceeding 400V/W (4×10³V/W) at room temperature and noise-equivalent power less than (0.5 nW/Hz^0.5), reference to the incident (absorbed) power. The performance is competitive with optimal coupled room-temperature terahertz detector and attributed to the fast carrier recombination driven by thermoelectric origin and high current gain, rather than the bolometric origin^6,7. Our analysis appealingly opens the perspective to properly engineering preferred photodetection mechanism for addressing the targeted THz application requirements.

© 2016 Optical Society of America