An Investigation of 10 MeV Electron Irradiation on Silicon NPN Transistors

The total dose effects of 10 MeV electron on the dc electrical characteristics of NPN bipolar junction transistors (BJT) were investigated in the dose range from 100 krad(Si) to 100 Mrad(Si). The key electrical parameters like Gummel characteristics, excess base current (Delta I-B = I-Bpost - I-Bpre), dc current gain (h(FE)), output characteristics(I-C-V-CE) and collector saturation current (I-CSat) were characterized in-situ during irradiation. After electron irradiation the base current (I-B) was found to increase significantly after irradiation and in turn decreases the hFE. The collector saturation region (I-CSat) was found to decrease with increase in the radiation dose. The electron irradiated results obtained are compared with Co-60 gamma irradiation in the same dose range. The observed degradation in the key electrical characteristics of the transistor is mainly due to radiation induced generation-recombination (G-R) centers in emitter-base (E-B) spacer oxide and point defects in the transistor structure. The degradation for Co-60 gamma irradiation was significantly less when compared to 10 MeV electron irradiated transistor.