An analysis of 100 MeV F8+ ion and 50 MeV Li3+ ion irradiation effects on silicon NPN rf power transistors

The dc characteristics exhibited by NPN power transistors are studied systematically before and after irradiation by 100 MeV F8+ ions and 50 MeV Li3+ ions in the dose range of 100 krad to 100 Mrad. The transistor parameters such as excess base current (ΔIB=IBpost–IBpre), dc current gain (hFE), transconductance (gm), and collector-saturation current (ICsat) were studied before and after irradiation. The damage factors (k) for hFE were calculated for ion irradiated transistors using Messenger–Spratt relation. The base current (IB) was found to increase significantly after ion irradiation and this in turn decreases the hFE of the transistors. The gm decreases significantly after ion irradiation. Moreover, the output characteristics of irradiated devices also show that the collector current (IC) in the saturation region (ICsat) decrease with increase in ion dose. The observed change in these characteristics may be due to the ion induced generation–recombination (G–R) centers in emitter-base (E-B) spacer oxide and the ion induced point defects and their complexes in the transistor structure.