Positron annihilation study of dopant effects on proton-irradiation defect in silicon

Abstract

Positron annihilation lifetime and doppler broadening measurements have been performed to examine the effects of B, Al and Ga dopants of Czochralski-grown Si (CZ-Si) on defects induced by 10MeV proton irradiations at room temperature with a total dose from 3×1012p/cm2 to 5×1014p/cm2. Isochronal annealing experiments were also carried out after the irradiations. In spite of the high-energy proton irradiation, a short lifetime component τ1 of about 100ps was observed in all of the specimens, which is considered to be responsible for dopant–oxygen–vacancy complexes. The long lifetime component becomes remarkable in specimens with irradiation more than 1014p/cm2. In isochronal annealing experiments, annealing stages at 527 and 552K were observed for the irradiated B doped CZ-Si with resistivities of 10 and 2Ωcm, respectively. This corresponds to the formation of larger vacancy clusters. We found that the formation of the vacancy–oxygen complex depends on the species of dopant atoms of silicon, especially at irradiation below 1014p/cm2.