Influence of Operating Conditions on Radiation Damage to Transistor Gain

Abstract

Gain degradation rates were obtained for various transistor operating conditions of current and voltage during Cobalt 60 irradiation and compared with the degradation rate for a radiation exposure in the passive state. The effects of emitter current alone, collector voltage alone, and normal transistor operating modes were studied. The results showed that increasing levels of carrier injection from the emitter caused decreasing rates of damage. For a 2N1613 type silicon transistor, the maximum reduction observed was approximately a factor of 2. This behavior is believed to be due to an alteration of the charge state of the radiation induced defect at the time the defect is formed. A lesser dependency with collector voltage was also observed. The effects of temperature in the range 105 F to 140 F, during gamma irradiation, were found to be small in comparison with the effects of active-passive current variations. Tests conducted in a neutron environment, where normal transistor operating modes were compared with the passive irradiation state, indicated very little influence upon damage rate.