Positron annihilation Doppler broadening measurements were conducted to characterize information of defects in 380keV Xe + -implanted aluminum upon thermal annealing at temperatures ranging from 100 to 600°C. The results suggest a broad distribution in the depth of vacancy-type defects in all the as-implanted samples. Meanwhile, with an increase in implantation dose the defect-rich region shifts toward the sample surface. It was found that increasing the annealing temperature triggers surface-directed migration and coalescence of vacancy and Xe n V m clusters in samples with implantation doses of 1E15 and 1E16 Xe + cm −2 . In the sample implanted with a high dose of 1E17 Xe + cm −2 , positron annihilation revealed a decomposition and even elimination of such defects under post-implantation annealing treatment.