Gunn Diode Simulator (2D): Space-Time Domain & v(E) Phase Plot

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 average drift velocity falls even as the field keeps rising — negative differential mobility. That makes a uniform current sheet unstable: a thin, self-amplifying high-field domain nucleates at the cathode and rides toward the anode, giving one current pulse per transit. This 2D companion simulator numerically integrates the same coupled continuity and Poisson equations as the 3D version — the same real GaAs velocity–field law, the same doping notch, the same live transit-time measurement — but renders it as a scrolling space-time waterfall of the field profile, a v(E) phase-space scatter that exposes the negative differential mobility directly, and a current oscilloscope trace, instead of a 3D bar chart.