Study on terahertz radiation generated by two dimensional electron gas plasma oscillation

The source and application of terahertz band have become the focus of current research, and many researchers have made important contributions. In the midst of this, the plasma instability of two-dimensional electron gas (2DEG) is a crucial physical mechanism for generating terahertz radiation in field-effect transistors, especially in high electron mobility transistors (HEMTs). In this paper, we will focus on two-layer 2DEG system, in which the two-stream instability is an important method that is expected to generate terahertz radiation. At present, most of the research on this subject is based on hydrodynamic models, focusing on the momentum conservation equation and continuity equation of current. However, the results obtained by using this approximate model must be deviated from the actual situation, and even produce a non-negligible difference in some cases. Therefore, we should use a more complete and more accurate equation to characterize this oscillation system, which is the Boltzmann equation. Hence, we use the semi-Lagrange method to achieve the mathematical description of Boltzmann equation, and use the Monte Carlo method to describe the collision integral term between electrons and electrons, and between electrons and phonons. Through the above method, we analyze the influence of different system parameters on the oscillation frequency, incremental rate, damping rate, etc. The convection intensity, that is, the difference of drift velocity of the two-layer two-dimensional electron gas, is analyzed, because the strength of convection intensity can significantly affect the threshold of instability. The interlayer thickness, because it can significantly change the coupling between the electrons of the double layer; The collision rate between electrons and phonons, because it strongly affects the decay of terahertz waves.