Gunn Diode Simulator: GaAs Transferred-Electron Domains

Gallium arsenide's conduction band has two very different valleys: a light, fast central (Γ) valley and a heavy, slow satellite (L) valley a few tenths of an eV higher. Push the field above roughly 3.2 kV/cm and hot electrons start scattering from the fast valley into the slow one — so, counter-intuitively, average drift velocity falls as the field keeps rising. That negative differential mobility makes a uniform current distribution unstable: a thin, self-amplifying high-field "domain" nucleates near the cathode and rides toward the anode at roughly the electron saturation velocity, giving a current pulse every transit — the basis of the GaAs Gunn diode oscillators used in radar and microwave transmitters mentioned throughout arsenide-nanomaterial literature. This simulator numerically integrates the coupled continuity and Poisson equations for a real GaAs velocity–field law and measures the live transit frequency, current density and peak domain field as you change bias, doping and device length.