Plasmons in Ballistic Nanostructures With Stubs: Transmission Line Approach

The plasma wave instabilities in ballistic field-effect transistors have a promise of developing sensitive terahertz detectors and efficient terahertz sources. One of the difficulties in achieving efficient resonant plasmonic detection and generation is assuring proper boundary conditions at the contacts and at the heterointerfaces and tuning the plasma velocity. We propose using the tunable narrow channel regions of an increased width, which we call “stubs” for optimizing the boundary conditions and for controlling the plasma velocity. We developed a compact model for terahertz plasmonic devices using the transmission line (TL) analogy. The mathematics of the problem is similar to the mathematics of a TL with a stub. We applied this model to demonstrate that the stubs could effectively control the boundary conditions and/or the conditions at interfaces. We derived and solved the dispersion equation for the device with the stubs and showed that the periodic or aperiodic systems of stubs allow for slowing down the plasma waves in a controllable manner in a wide range.