Power Amplification at THz via Plasma Wave Excitation in RTD-Gated HEMTs

We report studies of amplification arising from the dynamics of electron plasma waves in a high electron mobility transistor (HEMT) channel with injection from the gate exhibiting negative differential conductance (NDC). The gate NDC can be realized in a resonant tunnel diode (RTD) gate structure integrated in the HEMT. Though the electron plasma wave by itself cannot enable amplification, when coupled with gate NDC, they together form a gain medium at terahertz (THz) frequencies due to the higher plasma wave group velocity than the electron drift velocity. The analysis is developed using a distributed circuit model based on the Dyakonov-Shur hydrodynamic theory. Numerical and analytical results suggest that these devices can realize power amplification with a gain exceeding 5 dB while simultaneously providing conditional stability at THz frequencies.