Divacancies in undoped float-zone material were investigated, as a function of photon energies of between 0.2 and 1.2eV, by means of positron lifetime spectroscopy. Negatively-charged vacancies formed for photon energies of between 0.25 and 0.65eV, and above 0.75eV. On the other hand, in the 0.65 to 0.75eV range, there was no effect due to illumination. The results were explained in terms of the Watkins-Corbett divacancy model. Some evidence suggested that the radioactive positron source significantly reduced the stability of the photon-induced population of negatively charged divacancies, and this was used to explain some apparently anomalous results in the literature.

Positron Annihilation Study of Divacancies in Silicon Illuminated by Monochromatic Light S.Dannefaer, V.Avalos: Physical Review B, 1999, 60[3], 1729-33