Degradation of the power- and frequency-temperature performance of IMPATT diodes at lower frequencies

Investigations of the effect of ambient temperature on the RF power and frequency of
X
-band p+-n-n+ Si IMPATT diodes at frequencies and temperatures below their optimum conditions show considerable degradation of performance. A simple model is presented to explain these effects in terms of a lower limit to the instantaneous terminal voltage of the diode. Values of diode negative conductance are derived from the measurements and good agreement is obtained with independent measurements. The effects are relevant to both amplitude and frequency stability in wide band applications of IMPATT diodes.