Abstract
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.
Highlights
The terahertz (THz) wave has been widely applied in medicine, imaging, sensing, and communication.1–6 The THz source is significant in THz science and technology
In the 1990s, the theoretical research of Dyakonov and Shur has found that plasma waves are unstable in the channel of ballistic field effect transistors (FETs) with asymmetric source and drain boundary conditions,7 and it is called Dyakonov-Shur instability (DS instability)
According to the theory of DS instability, the channel of FETs is like a resonator, and the behavior of electrons is similar to shallow water and is investigated by the hydrodynamic model
Summary
The terahertz (THz) wave has been widely applied in medicine, imaging, sensing, and communication. The THz source is significant in THz science and technology. The quantum effects of the plasma wave must be considered in nanometer FETs, and the behavior of electrons is governed by quantum hydrodynamic (QHD) equations.. The DS instability is analytically and numerically investigated in a quantum gated cylindrical FET (see Fig. 1) by using two-dimensional QHD equations describing the behavior of electrons in the cylindrical coordinate system. The quantum effect, the pressure term, the wave vector of the circumferential direction, the drift velocity of the electron, the radius of the channel, and the length of the channel can influence plasma wave instability increment and oscillation frequency.
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