Redistribution of implanted oxygen in GaAs

We show that implanted oxygen in GaAs has two different thermal behaviours depending on the implantation dose. In the case of low doses, below 1014 oxygen-cm?2 oxygen diffuses very quickly at 900?C. In the case of high doses, above 1014 oxygen-cm?2, oxygen piles up around its projected range during annealing. This should be due to the formation of precipitates. The presence of substrate impurities in the nucleation process is not suspected.