The infra-red absorption of n- and p-type Ge crystals, enriched with 16O and/or 18O isotopes, was studied after 6MeV electron irradiation. The absorption spectra were measured at 10 and 300K. As well as known bands, which were characteristic of O-containing defects, new lines were detected at 669, 944 and 990/cm. These bands annealed out at 120 to 140C. A band at 621/cm, which had previously been related to the vacancy–O complex in Ge, annealed out simultaneously. The bands at 621 and 669/cm underwent identical temperature (10 to 300K) and O-isotope (16O to 18O) shifts. These bands were found to correspond to various charge states of a defect having an energy level near to Ev = 0.25eV. It was proposed that this defect was the vacancy–O complex (A center). Weak bands at 944 and 990/cm were identified as being combinations of asymmetrical stretching modes at 621 and 669/cm, with a symmetrical one at 320/cm, for neutral and negative charge states of the A center, respectively.

Local Vibrational Modes of the Oxygen–Vacancy Complex in Germanium. V.V.Litvinov, L.I.Murin, J.L.Lindstrom, V.P.Markevich, A.N.Petukh: Semiconductors, 2002, 36[6], 621-4