Admittance spectroscopy of silicon Zener diodes

The complex admittance of a range of Zener diodes with nominal breakdown voltages between 7.5 and 72 V was measured as a function of frequency between 10 Hz and 100 kHz and in the temperature range 70-300 K, with particular emphasis on the generally low loss component. Several spectral features were identified, including in some cases a high-temperature, low-frequency loss peak and in several cases a relatively 'flat' or frequency-independent loss, the amplitude of which may be dependent on temperature. No correlation could be found between the nominal value of the Zener voltage and the amplitude and spectral shape of the loss. On the other hand, a unique correlation was established between the magnitude of the loss and that of the DC conductance of all the diodes. Moreover, the loss peaks, where present, have the same activation energy as the DC conductances. The physical significance of these results is discussed briefly.