Evolution of vacancy-related defects upon annealing of ion-implanted germanium

Positron annihilation spectroscopy was used to study defects created during the ion implantation and annealing of Ge. Ge and Si ions with energies from 600 keV to 2 MeV were implanted at fluences between 1×1012 cm−2 and 4×1014 cm−2. Ion channeling measurements on as-implanted samples show considerable lattice damage at a fluence of 1×1013 cm−2 and a fluence of 1×1014 cm−2 was enough to amorphize the samples. Positron experiments reveal that the average free volume in as-irradiated samples is of divacancy size. Larger vacancy clusters are formed during regrowth of the damaged layers when the samples are annealed in the temperature range 200–400 °C. Evolution of the vacancy-related defects upon annealing depends noticeably on fluence of ion implantation and for the highest fluences also on ion species.