Dyakonov-Shur instability for terahertz electromagnetic radiation generation

Two decades ago, M.Dyakonov and M.Shur predicted the emission of THz electromagnetic (EM) radiation by simple transistors [1]. Their mechanism showed great potential as it uses a cheap to build and compact device. When submitted to a constant source-to-drain current and a constant gate-to-source voltage, hydrodynamical instabilities in small enough transistors should induce a spontaneous oscillation of the electron density field (plasma wave) inside their channels. The criteria for such instability are refined as compared to the original predictions in this paper. The extraction of independent constant is given allowing experimental verification. The more constraining conditions may explain the difficult observation of Dyakonov-Shur instabilities in experimental studies.