When the boundary conditions of the source and drain are asymmetric, the plasma waves may become unstable in the channel of a field effect transistor (FET). We use the quantum magnetohydrodynamic model to study the influence of the quantum Bohm potential, Fermi statistical pressure, and electron spin effects on the stability of THz plasma waves propagating perpendicular to the magnetic field in the FET. A dispersion equation governing the THz plasma oscillation is obtained. Numerical results have shown that the presence of spin effects has enlarged the instable range of β, enhanced the instability increment, and made the frequency of THz plasma waves larger. The research shows that nanometer FETs with spin effects have advantages in realizing practical terahertz radiation.
The instability of THz plasma waves propagating along a channel of field-effect transistors opens up a new mechanism of emission of THz waves. In this work, we investigate the instability of THz plasma waves in field-effect transistors in the presence of quantum effects and nonideal boundary condition at the source and the drain by using the quantum hydrodynamic model. The results show that the THz plasma waves will be unstable when the gate–source capacitances are larger than gate–drain capacitances and the instability increment can be increased by increasing gate–source capacitances or decreasing gate–drain capacitances. The results of this work give nano-field-effect transistors an advantage in achieving real THz oscillations.
Terahertz radiation can be generated due to the instability of terahertz(THz) plasma waves in field-effect transistors (FET). In this work, we discuss the instability of THz plasma waves in the channel of FET with spin and quantum effects under non-ideal boundary conditions. We obtain a linear dispersion relation by using hydrodynamic equation, Maxwell equation and spin equation. The influence of source capacitance, drain capacitance, spin effects, quantum effects and channel width on the instability of THz plasma waves under the non-ideal boundary conditions is investigated in great detail. The results of numerical simulation show that the terahertz plasma wave is unstable when the source capacitance is greater than the drain capacitance. This finding provides a new idea for finding efficient THz radiation sources and opens up a new mechanism for the development of THz technology.
The investigation on propagation of shock waves with terahertz frequency in field-effect transistors has promoted the development of terahertz radiators and detectors. In this paper, we analyze the nonlinear behavior of shock waves with THz frequency in field-effect transistors and study their propagation characteristics at different viscosity coefficients and times. Using reductive perturbation expansion, the hydrodynamic equations are reduced to a Burgers equation governing the characteristic of shock structures in field-effect transistors. We investigate the evolution of shock waves with different viscosity coefficients and times numerically. The analytical and numerical results show that there are monotone shock waves and oscillatory shock waves in this system and an increase in the viscosity coefficient will lead to the diminishment of oscillation. These properties could make the field-effect transistors advantageous for realization of practical terahertz radiation and detection.
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