Interstitial-related defect reactions in electron-irradiated oxygen-rich Ge crystals: A DLTS study

Electrically active defects induced in oxygen-rich Ge:Sb crystals by irradiation with MeV electrons at 80 or 300 K have been studied by means of capacitance transient techniques. Transformations of the defects upon post-irradiation isochronal anneals have also been investigated. It is argued that a radiation-induced electron trap with an energy level at about 110 meV below the conduction band edge (E110) can be associated with electron emission from an energy level of the Ge self-interstitial (IGe). The E110 trap is eliminated in the temperature range 150–200 K upon 15 min isochronal annealing. No other traps in the upper half of the gap emerge simultaneously with the disappearance of the E110 trap. It is argued that Ge self-interstitials become mobile at temperatures higher than 150 K and in oxygen-rich Ge interact with interstitial oxygen atoms (Oi). The resulting IGeOi complexes do not have energy levels in the upper half of the Ge gap. Diffusion and interaction of the IGeOi defects with interstitial oxygen atoms at T>50 °C result in the formation of IGeO2i complexes. In the most stable configuration the IGeO2i complex has orthorhombic (C2v) symmetry.