Terahertz electrodynamics in high electron-mobility transistors

Plasmon current, charge oscillations, and associated electromagnetic fields in the THz range of a two-dimensional electron gas forming the channel of a high electron mobility transistor have been analysed by solving the full set of Euler, continuity, and Maxwell equations. Upon imposing boundary conditions, a finite-length channel behaves as a plasmonic cavity exhibiting strong resonance effects when the wavelength is commensurate with the channel length. It is shown that, if the relaxation time is not exceedingly short, the resonance effects should survive and be detectable. The presence of a metallic gate has a strong effect on the longitudinal waves, by changing both dispersion relation and propagation velocity for modes of wavelength larger than the gate-channel separation. Furthermore, gate and channel behave as a planar transmission line that readily transfers the gate-source signal to the gate-drain load impedance. Finally, it is suggested that the non-linear nature of the Euler equation can explain the observation of mixing and detection upon application of THz excitations to high-electron-mobility transistors devices. (C) 2013 AIP Publishing LLC.