Terahertz detection and electronic noise in field-effect transistors

High electron-mobility transistors can be used as efficient detectors of an incident THz radiation on its metallic electrodes. This detection can become strongly resonant if the frequency of the THz radiation coincides with plasma eigenfrequencies of the transistor channel. By using a hydrodynamic model we investigate in parallel the transistor intrinsic high-frequency current noise spectrum and its harmonic and average current responses to a voltage perturbation at the electrodes. In both cases we discuss the appearance of resonances associated with the excitation of 2D and 3D plasma modes and, to get an additional physical insight into the properties of the different parts of the transistor, we compute also the local noise spectra originated by electron velocity perturbations distributed in the channel. We demonstrate that the main resonances in the drain current noise spectrum are the same as those observed in the current response to an external THz excitation thus confirming the strong link existing between these two quantities.