Gain and defect bi-stability in radiation damaged silicon bipolar transistors

Following irradiation, the gain of silicon bipolar transistors can be improved by annealing at 350 K. We show that both the number of defects measured by deep level transient spectroscopy (DLTS) and the gain can be restored to the post irradiation state by injection of minority carriers. One can cycle between the post irradiation state and the 350 K annealed state by alternating minority carrier injection at 300 K with zero- or reverse-bias anneals at 350 K. The structure of the bistable defects is not known, but we observe that they affect capture kinetics into the shallow charge state of the silicon divacancy defect, V2 (=/−). This suggests that the bistable defects are located within the neutron or ion damage cluster.