It was noted that the experimental temperature dependences of the carrier concentration in n-type crystals which were irradiated with 60Co γ-rays could not be described adequately in terms of O-vacancy complexes, when regarded as being a monovalent defect with one acceptor level at Ec-0.17eV. This could be achieved only within the framework of a 2-level model which assumed the existence of 2 independent monovalent defects, or of 1 divalent defect with levels having close energies. The analysis of published evidence suggested that an hypothesis which assumed that the A-centre was an amphoteric centre with acceptor levels at Ec-(0.15 to 0.16)eV and donor levels at Ec-(0.19 to 0.20)eV was the most reasonable. This then led to the conclusion that there existed a pair correlation between complexes that were generated by irradiation of O-V and Ci-Oi complexes.

Re-Evaluation of Energy Levels of Oxygen-Vacancy Complex in n-Type Silicon Crystals: Weak Compensation. L.F.Makarenko: Semiconductor Science and Technology, 2001, 16[7], 619-30