Measurement of d.c. negative resistance in avalanche diodes and its relation to anomalous-mode operation

Measurements of the current/voltage characteristics of semiconductor diodes beyond avalanche breakdown in which heating effects have been eliminated show that d.c. negative resistance is observed in qualitative agreement with theoretical calculations. Measurements of anomalous-mode oscillations on the same diodes show that, although d.c. negative resistance is often present at the current densities needed for anomalous-mode operation, it is not a necessary condition for high-efficiency oscillation.