Commercial npn transistor (2N 2219A) irradiated with 50 MeV Li 3+ -ions with fluences ranging from 3.1 · 10 13 ions cm À2 to 12.5 · 10 13 ions cm
À2, 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.
A commercial bipolar junction transistor (2 N 2219 A, npn), irradiated with 120 MeV Si 9+ ions with a fluence of the order of 10 12 ions cm −2 , is studied for radiation-induced gain degradation and deep level defects. I-V measurements are made to study the gain degradation as a function of ion fluence. Properties such as activation energy, trap concentration and capture cross section of deep levels are studied by deep level transient spectroscopy (DLTS). Minority carrier trap energy levels with energies ranging from E C − 0.160 eV to E C − 0.581 eV are observed in the base-collector junction of the transistor. Majority carrier trap levels are also observed with energies ranging from E V + 0.182 eV to E V + 0.401 eV. The identification of the defect type is made on the basis of its finger prints such as activation energy, annealing temperature and capture cross section by comparing with those reported in the literature. New energy levels for the defects A-center, di-vacancy and Si-interstitial are also observed. The irradiated transistor is subjected to isothermal and isochronal annealing. The defects are seen to anneal above 250 • C. The defects generated in the base region of the transistor by displacement damage appear to be responsible for transistor gain degradation.
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