A comparison of lower and higher LET heavy ion irradiation effects on silicon NPN rf power transistors

Abstract

The Silicon NPN rf power transistors were irradiated with 180MeV Au14+ and 150MeV Ag12+ ions in the dose range of 1Mrad to 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 (∆IB), dc current gain (hFE), transconductance (gm), displacement damage factor (K) and output characteristics were studied systematically before and after irradiation. These results were compared with lower linear energy transfer (LET) ions such as 50MeV Li3+, 95MeV O7+, 100MeV F8+, 140MeV Si10+ and 175MeV Ni13+ ions in the same dose range. The degradation for 180MeV Au14+ and 150MeV Ag12+ ion irradiated transistors was significantly more when compared to lower LET ions, indicating that the transistors are vulnerable to higher LET ion irradiations. Isochronal annealing study was conducted on the irradiated transistors to analyze the recovery in different electrical parameters. After isochronal annealing, the recovery in hFE and other electrical parameters was around 67% for Ag12+ ion irradiated transistors and 60% for Au14+ ion irradiated transistors.