An observed r.f. hysteresis characteristic of particular gunn diodes

Certain Gunn diodes, when mounted in half-wave resonant cavities, exhibited marked hysteresis in r.f. power when the bias voltage was increased above threshold and then reduced. Observations and measurements are described of the dependence on circuit loading of this phenomenon, and the associated I-V curve of the diode. Explanations of the phenomenon are proposed, based on recent investigations into the effect of imperfect cathode boundary conditions on the behaviour of Gunn devices. Some possible practical applications of the hysteresis are suggested, assuming that controlled manufacture of such devices might eventually be possible.