Small-Signal Characterization of FET/HEMT for Terahertz Applications

In recent years significant attention has been paid to the physical processes responsible for electron transport in modern field effect transistor (FET) and high electron mobility transistor (HEMT) channels. The final goal is to use them for various terahertz (THz) applications. For this sake the effects related to the excitation of two-dimensional (2D) plasma waves are considered as the most interesting phenomena at the moment. On the one hand, 2D plasma oscillations can lead to THz radiation emission and/or generation due to various plasma instabilities (for example, the so-called Dyakonov–Shur instability [1]). On the other hand, the excitation of 2D plasma waves can be used for THz signal detection which was recently observed experimentally in suband near-THz regions (see, e.g. [2] and references therein). Of course, for the analysis of the conditions favourable to realize these effects the knowlegde of the small-signal admittance and impedance of FET/HEMT structures interesting for THz applications is of great importance. The aim of this work is just to perform such an investigation through the calculation of the small-signal response of InGaAs HEMTs by using the hydrodynamic approach coupled with a pseudo-2D Poisson equation [2, 3].