Abstract
Vertical electrical transport in the heterostructure hot‐electron diode is considered theoretically. We present a simple dynamical model which consistently explains the measured S‐shaped negative differential conductivity in the current‐voltage characteristics. The model predicts a new type of self‐sustained 60 GHz voltage oscillations between tunneling and thermionic emission if the sample is driven by a dc voltage source having a resistor in series and a capacitor in parallel.