Aluminum implantation into (100) Si has been studied here by transmission electron microscopy (TEM), secondary ion mass spectrometry, and spreading resistance methods. For the implantation conditions (2×1015cm−2, 200 keV, room temperature) used in our experiments a buried amorphous layer is created from 50 to 300 nm below the surface. During N2annealing at 600–1000 °C, two discrete layers of dislocations at (110 and 330 nm) bounding a band of precipitates (>1011cm−2) were created, accompanied by a pronounced redistribution of Al in the implanted region. Three Al peaks at depths corresponding to the defect layers observed by TEM appeared. The positions and number of the peaks remained almost unaffected as a function of annealing temperature. High resolution TEM showed that the band of precipitate contained oriented Al particles and that these particles also nucleated on dislocations. The stability of the Al peak and associated low electrical activity (<10%) has been explained by taking into account the formation of Al precipitates and their interaction with the oxygen in the surrounding regions.