THz detection with field-effect transistors: The role of plasma waves and of thermoelectric contributions

Field-effect transistors owe their usefulness as detectors of THz radiation (TeraFETs) to their rectification capability. At low frequencies, the dominant mechanism is resistive mixing, supported at THz frequencies by the Dyakonov-Shur mechanism involving charge density waves in the transistor's channel. Additionally, a hot-carrier photo-thermoelectric effect can significantly contribute. We have developed a hydrodynamic transport model and implemented it in a commercial device simulator which handles these contributions on an equal footing. We show that thermo-electrics can significantly contribute not only in graphene TeraFETs but also in devices made from conventional semiconductors such as AlGaN/GaN TeraFETs. The simulations also allow us to address the question of why it has proven to be difficult to experimentally verify the signal enhancement by Fabry-Perot-like plasmon resonances in the channel predicted by Dyakonov and Shur to occur at high frequencies.