Room-temperature photoconduction assisted by hot-carriers in graphene for sub-terahertz detection

The terahertz (THz) technique is still confronted with challenges partly due to lack of an efficient method to achieve sensitive detection at room temperature. Gapless graphene is highly sought-after as a potential candidate for active material in photo-detection across the whole electromagnetic spectrum. However, the efficient photo-to-electric conversions within THz range are not well-developed at present. Here we report the hot carrier-assisted photoconduction being triggered by a sub-THz electromagnetic wave in homogeneous graphene, which is beyond the conventional interband mechanism and can be potentially extended to the higher THz band. The photoconductive effect here is attributed to the additional carriers replenished from the electrode following the potential disturbance of the hot carrier diffusion, which depletes or increases the sheet density in the channel depending on the carrier-polarity in the channel. The biased photoconductive device shows sensitivity over 400 V/W (4 × 10³ V/W) at room temperature and noise-equivalent power less than 0.5 nW/Hz^0.5 (20 pW/Hz^0.5) in reference to the incident (absorbed) power. The reported figures of merit represent the benchmark for further performance improvement via several different methods such as shortening the channel, using a matched antenna or material with improved mobility. All results presented open up the feasibility of achieving a photoconductive device for sensitive room temperature detection at terahertz frequencies.