DLTS study of deep level defects in Li-ion irradiated bipolar junction transistor

Commercial npn transistor (2N 2219A) irradiated with 50 MeV Li3+-ions with fluences ranging from 3.1 × 1013 ions cm−2 to 12.5 × 1013 ions cm−2, is studied for radiation induced gain degradation and minority carrier trap levels or recombination centers. The properties such as activation energy, trap concentration and capture cross section of induced deep levels are studied by deep level transient spectroscopy (DLTS) technique. Minority carrier trap levels with energies ranging from 0.237 eV to 0.591 eV were observed in the base–collector junction of the transistor. In situ I–V measurements were made to study the gain degradation as a function of ion fluence. Ion induced energy levels result in increase in the base current through Shockley Read Hall (SRH) or multi-phonon recombination and subsequent transistor gain degradation.