Impurity-vacancy complexes in electron-irradiated silicon

A comprehensive study of 2.5--10-MeV electron-irradiated Czochralski Si has been conducted using positron lifetime and Doppler broadening spectroscopies. Eight samples, ranging from heavily doped n type to heavily doped p type, were irradiated simultaneously at room temperature to facilitate quantitative comparisons between the samples. The influence from the oxygen impurity was also investigated by comparison with oxygen-free Si. For lightly doped materials (dopant concentration less than 5×10¹⁶/cm³) the irradiation damage is dominated by free, and negatively charged divacancies for the dose employed in this work (1.2×10¹⁸e^-/cm²). For the heavily doped materials (dopant concentrations larger than 5×10¹⁷/cm³) vacancy-dopant complexes dominate, some of which involve divacancies, and in these samples very high introduction rates (1--4cm^-1) are estimated. In heavily B-doped materials evidence is found for thermally activated trapping by boron divacancy complexes. Association of divacancies with P, Sb, and B dopants was found to modify significantly the Doppler S parameter relative to the value for free divacancies.