Samples of O-doped material were irradiated with 2MeV electrons and were isochronally annealed at between 80 and 440C. A total of 64 local vibrational mode bands arising from O-related defects were observed in the infra-red absorption spectrum, of which 23 belonged to thermal donors. Two bands (621.6 and 669.1/cm) at 5K were attributed to VO0 and VO–, respectively; thus implying that the stretching mode of the A center in Ge was charge-state dependent - similar to the A center in Si. Bands at 525.5, 780.3 and 817.9/cm (5K) were attributed to 3 modes of the O dimer. The wave-number positions were in excellent agreement with the corresponding modes in Si, and with published ab initio calculations of the dimer in Ge. Irradiation resulted in the enhanced formation of dimers and thermal donors. Annealing data on the dimer and the early thermal donor bands supported a model in which the dimer was the first step in the O agglomeration sequence of thermal donor formation. Preliminary results were also obtained concerning the Ge-isotope splitting of some of the absorption bands.

Local Vibrational Mode Spectroscopy of Dimer and Other Oxygen-Related Defects in Irradiated and Thermally Annealed Germanium. P.Vanmeerbeek, P.Clauws: Physical Review B, 2001, 64[24], 245201 (6pp)