Terahertz plasma wave generation in ultrashort-channel field effect transistors: The essential role of carrier drift velocity saturation

Taking into account both the carrier scattering and the velocity saturation, we examine the plasma wave instability of the high-density two-dimensional electron gas in a field effect transistor. It is shown that both the carrier scattering and the velocity saturation lead to a strong damping of the plasma wave instability. A threshold diagram of the instability is calculated. The device parameters required for a plasma wave generation are shown to be more strict than those reported in up-to-date subterahertz emission experiments.