Device Simulation of the Dyakonov-Shur Plasma Instability for THz Wave Generation

Abstract

Dyakonov and Shur suggested electron-plasma instabilities in the channel of HEMTs as new sources for THz waves that could fill the THz gap. Their analytical model was based on the Euler equation and Dirichlet boundary conditions for the electron density at the source side of the channel and for the current density at the drain side. There have been many attempts to solve the equations for realistic devices by numerical simulation, where the boundary conditions between the channel and the highly doped source/drain regions (ohmic contacts) are a result of the device simulations. The only boundary conditions, that can be specified in the device simulations are the ones between the highly doped regions and the terminals. It turned out that these boundary conditions have a strong impact on the plasma resonances in the HEMT and the resonances vanish, if the device is simulated by the more physics-based Boltzmann transport equation in conjunction with thermal bath boundary conditions. The lack of plasma instabilities in these simulations is matched by experiments, in which no clear indications of instabilities could be found.