At low dose rate

ionizing radiation response of NPN bipolar transistors at different base-emitter junction bias

i.e

negative bias

positive bias and zero bias

was investigated in this paper. Under low dose rate irradiation of up to 1 kGy by 60Co γ-rays

the NPN bipolar transistors at different bias behaved differently. An NPN bipolar transistor in irradiation with negative biased at the base-emitter junction

the excess base current and gain degradation were much larger than those of the other two bias situations

and the excess base current and gain degradation were minimal when the base-emitter junction was positively biased. Possible mechanism was discussed.