Investigation of the Dyakonov-Shur instability for THz plasma waves in quantum gated cylindrical FET

Plasma waves may become unstable in the channel of field effect transistors (FETs) with asymmetric boundary conditions on source and drain, which is known as Dyakonov-Shur instability. In this letter, we extend the Dyakonov-Shur instability to the quantum gated cylindrical FET and obtain the dispersion equations describing unstable terahertz (THz) plasma waves using quantum cylindrical hydrodynamic equations. Research results show that the length of the channel and the wave vector of the circumferential direction inhibit the instability increment; however, the quantum effect, the radius of the channel, and the electron temperature enhance the instability increment. The oscillation frequency increases with the increase in the quantum effect, the wave vector of the circumferential direction, and the electron temperature, but the oscillation frequency increases with the decrease in the length and radius of the channel. Compared with the one-dimensional rectangular FET, THz plasma waves in the two-dimensional cylindrical FET have a higher oscillation frequency.