Research On Radiation And Annealing Effects Of NPN Transistors

The degradation caused by low energy protons and electrons are examined for the NPN transistors (3DG112D). The current gain is one of the most important parameters of bipolar junction transistors (BJTs). The degradation of the current gain for transistor is significant and typical radiation damage effect. The electrical parameters of NPN transistors are measured during the irradiation. After irradiation, the changes in current gain with annealing time, temperature and bias are investigated.The results show that, with increasing the irradiation fluence, the trends of degradation in electrical parameters of NPN transistors are similar, under the irradiation of different particles, fluxes and energies. When the NPN transistors are irradiated by 110keV, 70keV electrons and 70keV protons, the reciprocal of the current gain of NPN transistors increases and is gradually saturated with increasing the fluence. When the NPN transistors are irradiated by 170keV, the reciprocal of the current gain of NPN transistors increases linearly with the irradiation fluence. The damage irradiated by both 110keVelectrons and 170keV protons at the same time is more serious than that by just one kind of irradiation sources.Based on the annealing effects research, the current gain of the NPN transistor is gradually recovered with time during isothermal annealing, while the higher the temperature, the larger the annealing velocities during isochronous annealing. Moreover, the annealing will be accelerated, if the emitter is negative biased. However, there will be little influence if the emitter is positive biased. On the other hand, the annealing effect is also affected by the irradiation sources. The ionization damage caused by low energy electrons could disappear with relatively low annealing temperature (300℃). The damage induced by low energy protons will not be removed entirely even with rather high the temperature (500℃).