Intrinsic photo-conductance triggered by the plasmonic effect in graphene for terahertz detection

Terahertz (THz) technology is becoming more eminent for applications in diverse areas including biomedical imaging, communication, security and astronomy. However, THz detection still has some challenges due to the lack of sources and detectors despite decades of considerable effort. The appearance of graphene and its gapless spectrum enable their applications in sensitive detection of light over a very wide energy spectrum from ultraviolet, infrared to terahertz. Several mechanisms in graphene for THz detection have been proposed, such as photo-thermoelectric, Dyakonov-Shur (DS) and bolometric effects. Here, we propose a photoconductive mechanism assisted by plasma wave in a graphene field-effect transistor (FET). Sensitive response to THz radiation can be realized far below the interband transition at room temperature. The response is due to the contributions of both plasma drag and convection effects. The two effects can both trigger multiple potential wells along the channel, which are different from other quantum-transition mechanisms. The photoconductive effects can be explored in both periodic and non-periodic systems and can be substantially enhanced under the electric field. They could reduce the burden of structural complexity compared to other mechanisms like unilateral thermoelectric and DS detection. This paves the way for more judicious photo-detector design for versatile THz applications.