Efficient terahertz mixer from plasma wave downconversion in InGaAs HEMT

摘要

Two-dimensional (2D) plasma waves in field effect transistors are well known since the pioneer work of Dyakonov and Shur. The application to terahertz (THz) detection was proven recently both at cryogenic and room temperatures. Aside from these experiments, we used the interband photoexcitation brought by the difference-frequency component of a photomixed laser beam to excite very efficiently plasma waves in HEMT channel at room temperature. Owing to a specific experimental setup avoiding unwanted high-frequency electrical oscillations of the HEMTs, we obtained the spectral profiles of THz 2D plasma waves resonances of InGaAs HEMTs for many experimental conditions. The effect of geometrical HEMTs parameters (lengths of the gate and surrounding regions) as well as biasing conditions (drain and gate voltages) was evaluated on both plasma oscillations frequencies and amplitudes. Simultaneously, a numerical approach, based on hydrodynamic equations coupled to a pseudo-2D Poisson solver, was developed that compares well with experiments. Using this unique combination of experiments and numerical simulations, a comprehensive spectroscopy of plasma waves in HEMTs is thus obtained. It provides a deeper insight into the physical processes involved in plasma wave excitation and allows predicting for mixer operation at THz frequency only using the plasma wave nonlinearity. Mixing experiments are under progress.