Effect of aging on radiation response of bipolar transistors

A thermally activated aging process is investigated by experimental evaluation of the change in radiation response of test PNP and NPN transistors over a wide range of emitter-base bias conditions after preirradiation elevated-temperature stress and infrared illumination. A comparison of radiation response after temperature stress for transistors with rather different ages is investigated. For "young" transistors, zero change (zero aging) in radiation response after elevated temperature stress at some emitter-base bias was observed. A qualitative physical model is offered to explain the experimental results. The model is based on effect of electron trap accumulation during elevated-temperature stress. Short-time infrared illumination provides effects similar to preirradiation long-term temperature stress and annealing of irradiated devices at elevated temperature.