Terahertz response mechanisms in graphene-based photodetector devices

Novel gapless two-dimensional materials are ideally suited as efficient broadband photodetectors due to the absence of a fundamental lower energy threshold. Graphene, with its exceptional electronic properties has emerged as a prominent platform for detecting frequencies in the terahertz (THz) spectrum, offering technical advantages by simplifying system designs and removing the need for complex optical components. Graphene field effect transistors (GFET) exhibit room temperature broadband photoresponse to incoming sub-THz radiation, thanks to the photothermoelectric and plasma wave rectification. We present a detailed analysis on the sub-THz response in a high-quality asymmetrically dual-gated few-layer graphene device. Our study identifies the different THz response mechanisms in graphene multi-gate detectors that contribute to the photothermoelectric effect (PTE) and the Dyakonov-Shur (DS) effect tunable by temperature, frequency, and gate voltage. The experimental results verify quantitatively the relevance of the thermoelectric contribution to the overall rectification and the measured photocurrent, which allows for more accurate modelling of the GFET THz detectors.