To study both generation rates and mobilities of point defects due to electron irradiation, we measured and analyzed optical-absorption spectra of complexes of hydrogen and point defects generated by low-temperature electron irradiation of hydrogenated Si crystals. Specimens were doped with H by heating in H 2 gas at 1300°C followed by quenching. They were then irradiated with 6-MeV electrons at 270, 200, 130, and 77 K. We measured their optical-absorption spectra at 7 K with an Fourier transform infrared spectrometer. We observed many optical absorption peaks which are due to localized vibrational modes of H bound to various point defects. The irradiation temperature dependence of concentrations of some H-point defect complexes was not monotonic contrary to the prediction of metastable Frenkel pair models. Relative intensities of those peaks depended on the irradiation temperature and were interpreted to be due to the relative mobilities of various point defects. The migration energies of a self-interstitial and a Frenkel pair relative to that of a vacancy were determined.
In order to obtain information on the degradation of solar cells in artificial satellites as a result of cosmic ray radiations, positron annihilation lifetime experiments were performed for B-doped p-type Czochralski (CZ) silicon wafers irradiated at room temperature with 1 MeV electrons with fluences between 10 14 and 10 17 e/cm 2 . Positron lifetime measurements were done at 100 K to improve the trapping rates of positrons with defects. The mean lifetime of irradiated Si was shorter than that of unirradiated Si. We found that short lifetime defects (approximately 100 ps) existed, which could be associated with complexes of Si with interstitial oxygen atoms, doped B and vacancies resulting from irradiation. Lifetime components longer than those of the bulk accounted for the formation of thermal donors and divacancies.
Positron annihilation lifetime experiments have been performed for B-doped p-type Czochralski silicon (CZ-Si) wafers irradiated at 300 K with 1 MeV electrons with fluences between 10 14 and 10 17 e/cm 2 . In order to examine the thermal behavior of defects having shorter lifetime than that of the bulk, isochronal annealing experiments were carried out from 300 K to 900 K. The measurements were performed at 100 K to improve the positron trapping rates for defects. It is found that components having longer lifetime than that of the bulk behave differently, and they comprise by thermal donors (TD) and divacancies (V 2 ). The short-lifetime component observed in the present experiments is responsible for a complex defect with impure interstitial oxygen atoms, doped B atoms and vacancies. The short-lifetime defects change into vacancy-type defects and thermal donors in certain ranges of annealing temperatures.
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