Recombination Centers in Gamma-Irradiated Silicon

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Abstract
The minority carrier lifetime in gamma‐irradiated silicon crystals was studied. The doping impurity was phosphorus, arsenic, or boron, and the crystals were either float‐zoned or pulled from the melt. The silicon E center was found to be the dominant recombination center in float‐zoned, n‐type crystals after irradiation. The capture cross section of the center for holes was measured to be 1.1×10−13 cm2 in phosphorus‐doped silicon. The activation energy for annealing of an E center has been reported to be 0.94 eV, and the corresponding activation energy for the annealing in arsenic‐doped crystals was found to be 1.5 eV. After annealing at 160°C, where the E center is known to anneal, the existence of some other energy level at about 0.4 eV below the conduction band was detected. In crystals other than float‐zoned n‐type, the A center governed the recombination. The cross section of this center was found to be 1.5×10−14 cm2 for holes and 2×10−16 cm2 for electrons. The introduction rate of the A center was found to be the same for a variety of samples. The value was 1.3×10−3 defects/cm3 per photons/cm2.