Oxygen defects in irradiated germanium

The defects present in oxygen-rich irradiated germanium have been extensively characterised from an experimental point of view. Here, we summarise recent theoretical findings obtained using the cluster method and discuss their relation with the experimental data. In order to find a microscopic interpretation of the reactions taking place in this material upon annealing up to 400°C, we performed nudged elastic band (NEB) calculations of the migration and dissociation paths of VO, as well as a modelling of other oxygen-related complexes that are expected to form in this temperature range. Energy barriers of 1.5 (1.1) eV and 1.2 (0.9) eV for the dissociation and migration of the neutral (negatively charged) VO defect are found. We compare these with the activation energies estimated from the analysis of Hall effect, deep level transient spectroscopy (DLTS) and infra-red (IR) spectroscopy annealing data reported in literature.