Influence of high-energy electron irradiation on the formation and annihilation of the photoluminescence W center and the center's origin in a proton-implanted silicon crystal

The population change of the photoluminescence (PL) W center (or I l center) with 2-MeV electron irradiation in proton-implanted silicon crystal was observed to investigate the origin of the center. While a straightforward annihilation of the W centers formed by proton implantation with an increase of the electron fluence was observed in the low fluence region, the number of centers increased in the high fluence region (>2 X 10 1 8 electron/cm 2 ) due to the predominance of formation over annihilation. The annihilation and formation of the W centers were analyzed as first and second order with respect to the numbers of vacancies and self-interstitials, respectively. The efficiency of the W-center formation from element pairs produced by electron irradiation was much smaller than that for ion implantation. Considering the findings obtained in the present study and those given by other studies, the split monointerstitial and the ST di-interstitial (ST: split triple) were chosen as the probable candidates for the W center.