New gamma-radiation damage centres observed in germanium by deep level transient spectroscopy

The dominant defect levels in γ-irradiated doped and high purity Ge have been studied by transient capacitance spectroscopy. All p-type samples displayed acceptors at Esub(v) + 0.23 eV and Esub(v) + 0.38 eV, whose capture cross-sections for holes were approximately 10-14 cm2. In n-type samples a deep donor (Esub(c) - 0.42 eV) with electron capture cross-section approximately 10-14 cm2 was observed in all but the highest purity material. Long-term room temperature annealing introduced two deep donors (Esub(c) - 0.36 eV, Esub(c) - 0.20 eV) into some n-type material; newly irradiated samples from the same crystals did not show these levels. In the n-type material, the loss of shallow donor states by electrically inactive complexing with vacancies was the compensation mechanism. (author)