Dependence of ionizing radiation induced hFE degradation on emitter periphery

The current gain (h
FE
) of planar bipolar transistors degrades when such devices are exposed to ionizing radiation because of the increase in the base surface current. This increase is due to two phenomena that are a result of the interaction of the radiation and the passivation layer over the base: 1) positive charge accumulation in the passivation layer, generally near the semiconductor-insulator interface, and 2) creation of fast surface states at the interface.
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