EPR of a carbon-oxygen-divacancy complex in irradiated silicon

Additional EPR experiments on the Si-G15 spectrum, previously observed in p-type, pulled silicon after electron irradiation, are described. The hyperfine interaction with the 29Si nuclei and the quenched-in defect alignment under uniaxial stress are newly observed. A correlation is made between the G15 spectrum and the C(3) infrared absorption band at λ = 11.6 μm via the defect symmetry, stress response and their dependence on irradiation temperature and electron-fluence. Based on the new experimental results as well as existing results from the infrared and EPR studies, the G15 spectrum is identified as arising from a positive charge state of a defect which may be viewed as a carbon-oxygen molecule bonded within a divacancy. The trapping of a mobile interstitial carbon by a [vacancy ± oxygen] pair results in the formation of the [CO ± V2] complex and the liberation of a selfinterstitial at room temperature. The electrical level of G15 is determined to be (Ev ± 0.32) eV. Tentatively the G16 spectrum is identified as being due to the negative charge state of this defect and having an electrical level at (Ec — 0.43) eV.