Ionization and Displacement Damage in Silicon Transistors

An investigation of electron-induced ionization and displacement damage in N-P-N and P-N-P transistors at medium and low powers is presented. Measurements of base and collector currents as a function of base-emitter voltage with radiation as a parameter were made. The transistors were irradiated sequentially with 125 keV and 1 MeV electrons. Initial saturation of surface-damage effects with 125 keV made possible the separation of displacement and surface damage. The results show that the dominant displacement damage occurs within the emitter-base transistor region for fluence levels less than or equal to 5×1015 1 MeV e/cm2 and emitter currents less than or equal to 10 milliamperes in the 2N2102 and 2N1132 transistors. Above this fluence level, displacement damage in the bulk of the base region becomes effective. Isochronal and isothermal annealing measurements indicate that the results can be explained by attributing the damage in the transistion region to recombination current losses at K-centers for N-P-N transistors and A-centers for P-N-P transistors.