Swift heavy-ion irradiation effects on electrical and defect properties of NPN transistors

Abstract

NPN transistors were irradiated by 95 MeV oxygen ions in a fluence ranging from 5 × 1010 to 5 × 1012 ions cm−2. The dc current gain (hFE), excess base current (ΔIB = IBpost − IBpre), excess collector current (ΔIC = ICpost − ICpre) and collector-saturation current (ICS) of the ion-irradiated transistors were studied systematically. We found that both hFE and ICS of the transistors decrease drastically after ion irradiation. Secondly, a significant increase in the collector current (IC) along with the increase in the base current (IB) after ion irradiation was observed. The radiation-induced trap levels in the collector–base depletion region of NPN transistors were studied by employing the deep level transient spectroscopy technique and different types of trap levels were observed. The results obtained on the activation energy, density of trap levels, apparent capture cross section of the defects, introduction rate and space charge layer lifetime of different defects for different total fluence are presented and discussed.