Current-Driven Dyakonov-Shur Instability in Ballistic Nanostructures with a Stub

We develop a compact model for the THz plasmonic unstable structures with tunable narrow-channel regions of an increased width (called plasmonic stubs) using the transmission line analogy and derive the dispersion equations describing unstable plasmons. The solutions of the dispersion equations in the plasmonic systems with the electron drift, which are derived using the hydrodynamic model and generalized to account for the stubs, illustrate the device physics and can be used for design and characterization of THz plasmonic-electronic sources. Our results show that adding stubs allows one to control the Dyakonov-Shur instability in plasmonic field-effect transistors by optimizing the boundary conditions, controlling the plasma velocity, and making it possible to drive periodic plasmonic structures wirelessly, thus avoiding the contact problems.