Evidence for a vacancy?phosphorus?oxygen complex in silicon

Low-energy (~0.5?MeV) electrons arising from 60Co??-irradiation were used to create phosphorus?vacancy (PV) pairs and oxygen?vacancy pairs in Czochralski-grown Si. Positron annihilation data show that PV pairs anneal in two stages: the commonly observed stage around 125??C, where one third of the pairs disappear with an activation energy of 0.8 ? 0.2?eV, and a new stage where none disappear, but form PV?oxygen complexes with an activation energy of 2.0 ? 0.2?eV.