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

• The effects of 80 MeV Au14+ and 150 MeV Ag12+ ions on Si NPN transistors are studied.
• Lower LET Results are compared with lower LET ion irradiation results.
• Ionization and displacement damages of ions in transistors are simulated using SRIM.
• Higher LET ions degrade dc characteristics more when compared to lower LET ions.
• Isochronal annealing study was conducted on the irradiated transistors.
• After annealing, the recovery in hFE and other electrical parameters are significant.

The Silicon NPN rf power transistors were irradiated with 180 MeV Au14+ and 150 MeV Ag12+ ions in the dose range of 1 Mrad to 100 Mrad. 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 50 MeV Li3+, 95 MeV O7+, 100 MeV F8+, 140 MeV Si10+ and 175 MeV Ni13+ ions in the same dose range. The degradation for 180 MeV Au14+ and 150 MeV 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.