On the Simulation of Plasma Waves in HEMTs and the Dyakonov-Shur Instability

Abstract

Modeling of plasma waves in HEMTs by momentsbased transport models is investigated. The balance equations are derived from the Boltzmann transport equation by projection onto Hermitian polynomials. The discretized equations are stabilized by an approach based on matrix exponentials, which in the case of the drift-diffusion model reproduces the Scharfetter-Gummel stabilization. Simulations of a realistic HEMT show that plasma instabilities are rather unlikely to occur and that effects not considered by Dyakonov and Shur (e.g. real ohmic contacts) strongly damp the THz waves. Furthermore, quasi-ballistic transport can not be captured by higher-order models.