Oxygen-vacancy defects in electron-irradiated Si: the role of carbon in their behavior

This is a detailed study of the effect of carbon impurity on the production of the oxygen-vacancy (VO) pair and its conversion to the VO2 defect, in electron-irradiated Czochralski silicon material, by means of infrared spectroscopy. Upon irradiation vacancies are trapped by oxygen atoms to form VO pairs and it was determined that the presence of carbon enhances the production of this pair. This is attributed to the tendency of carbon to capture self-interstitials, thus decreasing the annihilation rate between vacancies and self-interstitials produced during the irradiation and therefore increasing the availability of vacancies to pair with oxygen atoms in the course of irradiation. Upon annealing a number of VO pairs are captured by oxygen atoms to form VO2 defects. It was determined that the percentage of the VO converted to the VO2 defects decreases as the concentration of carbon increases. The phenomenon is discussed in terms of the various reaction channels that VO pair participates upon annealing and how the presence of carbon impacts the balance between these reactions, affecting the final products of the involved processes. Finally, an opposite trend for the conversion of the VO2 to the VO3 defect was observed. The percentage of VO2 converted to VO3 is enhanced with the increase of carbon content. This finding is discussed in terms of the effect of carbon in the oxygen diffusivity and the final impact on the reaction VO2 + Oi → VO3.