Investigation of deep level defects in copper irradiated bipolar junction transistor

Abstract

Commercial bipolar junction transistor (2N 2219A, npn) irradiated with 150MeV Cu11+-ions with fluence of the order 1012ionscm−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. The 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 levels with energies ranging from EC−0.164eV to EC−0.695eV are observed in the base–collector junction of the transistor. Majority carrier trap levels are also observed with energies ranging from EV+0.203eV to EV+0.526eV. The irradiated transistor is subjected to isothermal and isochronal annealing. The defects are seen to anneal above 350°C. The defects generated in the base region of the transistor by displacement damage appear to be responsible for transistor gain degradation.