Plasma waves subterahertz optical beating detection and enhancement in long-channel high-electron-mobility transistors: experiments and modeling

A photomixed laser beam of two 1.55 μm continuous-wave (CW) lasers is used for interband photoexcitation in submicron gate length InAlAs/InGaAs transistors. Results show the clear excitation of plasma oscillation modes in the transistor channel. A strong amplification of the optical beating detection in the 0–600 GHz range is observed as a function of drain–source voltage. Numerical results, using hydrodynamic model coupled to a pseudo-2-D Poisson equation, are in good agreement with experiments concerning the plasma frequency dependence with gate voltage. Moreover, this model confirms both optical beating detection at subterahertz frequencies and the enhancement observed when drain–source voltage increases.