Defect evolution in MeV ion-implanted silicon

Lightly doped silicon samples of both n- and p-type, have been implanted with low doses of H, B and Si ions using energies between 1 and 6 MeV. The resulting electrically active point defects were characterized by deep level transient spectroscopy (DLTS) and several of these defects involve oxygen and/or carbon, two major impurities in as-grown crystalline silicon. Both interstitial- and vacancy-type defects are observed; in particular, interstitial carbon is found to migrate at room temperature with a diffusion constant of similar to 1x10(-15) cm(2) s(-1) and is effectively trapped by interstitial oxygen atoms. The concentration of implantation-induced defects increases linearly with dose but the defect production decreases at high enough dose rates, This dose rate effect depends on the ion mass and is qualitatively predicted by computer simulations of the defect reaction kinetics.