Effect of spin on the instability of THz plasma waves in field-effect transistors under non-ideal boundary conditions

Terahertz (THz) radiation can be generated due to the instability of THz plasma waves in field-effect transistors (FETs). In this work, we discuss the instability of THz plasma waves in the channel of FETs with spin and quantum effects under non-ideal boundary conditions. We obtain a linear dispersion relation by using the 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 THz plasma wave is unstable when the drain capacitance is smaller than the source capacitance; the oscillation frequency with asymmetric boundary conditions is smaller than that under non-ideal boundary conditions; the instability gain of THz plasma waves becomes lower under non-ideal boundary conditions. This finding provides a new idea for finding efficient THz radiation sources and opens up a new mechanism for the development of THz technology.