Annihilation of Positrons in Electron‐Irradiated Silicon Crystals

Abstract Lifetime and Doppler‐broadening measurements in positron annihilation are used to investigate defects in silicon crystals irradiated with electrons of 1 MeV energy. The lifetime in undoped defect‐free Si is found to be (218 ± 8) ps. Isochronal annealing studies in the temperature range 12 K < T a < 600 K show that in undoped Si at low temperature positrons annihilate at neutral monovacancies and double vacancies with lifetimes of (266 ± 10) and (318 ± 15) ps, respectively. In boron‐doped crystals before and after irradiation no special defect reveals in the spectra up to 400 K. This result is explained by the different charge of the defect states in the doped Si. The mean lifetime in doped crystals amounts to (233 ± 10) ps.

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