Behaviour of oxygen-related thermal donors in Ge crystals Czochralski-grown from the melt covered fully by B₂O₃

Oxygen-related thermal donors (OTDs) in oxygen-enriched Czochralski Ge crystals grown from a melt fully covered by B₂O₃ liquid were investigated by infrared spectroscopy. Interstitially dissolved oxygen concentrations [O_i] and thermal donor concentrations N_TD in Ge specimens annealed at 350°C for 64h and at 550°C for 1h, followed by subsequent fast cooling to room temperature, were measured in comparison with those in as-grown Ge. By annealing at 350°C, an absorption peak developed at 780 cm^-1 and the peak height at 855 cm^-1 related to [O_i], decreased. The absorption coefficient at 780 cm^-1 showed the same correlation to the difference between the total concentration of oxygen atoms and the dissolved oxygen concentration in the annealed specimens. It was found that the number of oxygen atoms forming the OTD increases with increasing annealing time at 350°C.