The effects of high-energy ion irradiations on the I-V characteristics of silicon NPN transistors

The silicon NPN rf power transistors were irradiated with different linear energy transfer (LET) ions such as 50MeV Li3+, 80MeV C6+ and 150MeV Ag12+ ions in the dose range of 1-100Mrad. The SRIM simulation was used to understand the energy loss and range of these ions in the transistor structure. The different electrical parameters such as Gummel characteristics, excess base current (I-B), DC current gain (h(FE)), displacement damage factor (K) and output characteristics were systematically studied before and after irradiation. The ion irradiation results were compared with Co-60-gamma irradiation result in the same dose range. A considerable increase in base current (I-B) and a decrease in h(FE) and I-CSat were observed after irradiation. The degradation in the electrical parameters was comparably very high for Ag12+ ion-irradiated transistor when compared to other ion-irradiated transistors, whereas the degradation in the electrical parameters for Li3+ and C6+ ion-irradiated transistors was comparable with gamma-irradiated transistor. The isochronal annealing study was conducted on the 100Mrad irradiated transistors up to 500 degrees C to analyze the recovery in different electrical parameters. The h(FE) and other electrical parameters of irradiated transistors were almost recovered after 500 degrees C for 50MeV Li3+, 80MeV C6+ ion and Co-60-gamma-irradiated transistors, whereas for 150MeV Ag12+ ion-irradiated transistor, the recovery in electrical characteristics is not complete.