Low Dose Ionization-Induced Failures in Active Bipolar Transistors

Gain degradation under different conditions of applied voltage and injection current during low dose gamma irradiation by a Cobalt-60 source was examined for the 2N1613, 2N2102 and 2N3799 type transistors. For transistors biased during irradiation, the gain degradation was greater for higher collector-base voltages applied during irradiation, and the gain degradation was less for higher emitter current levels during irradiation. However, the dependence of gain degradation on current during irradiation was small for the 2N1613, and the dependence of gain degradation on voltage during irradiation was small for the 2N3799. Several methods of data presentation are used. The presentation of the gain degradation in terms of percent remaining gain is found to facilitate intercomparison of results and to provide a format which is readily applicable to design problems. The method of normalization of the data to give the percent remaining gain is analyzed and is demonstrated to be justified. When expressed as a percentage, the degradation of low gain transistor types is as significant as the high gain transistor type at the same total dose with bias present during irradiation.