A quantitative investigation of divacancy production enhancement by interstitial oxygen in electron-irradiated silicon

Czochralski silicon samples containing different amounts of interstitial oxygen were irradiated with 2-MeV electrons at room temperature to a fixed dose of 1.0x1018 electrons/cm2. Prior to irradiation the interstitial oxygen content of similar specimens had been varied by precipitating different amounts of the dispersed oxygen by suitable heat-treatments. We find that the introduced divacancy density depends linearly on the interstitial oxygen concentration in the samples. However, the divacancy concentration correlates better to the density of introduced vacancy-oxygen centers than to the initially present dissolved oxygen concentration. Based on our experimental data we propose different models for the oxygen enhancement of the divacancy production rate. Numerical tests of these models were performed. A model in which oxygen is allowed to capture both vacancies and interstitials can reproduce all the experimental observations. (orig.)