Al/Si is probably the most widely investigated metal semiconductor structure ever examined. This work studied the effects of Al-recoil implantation into n-type Si using Ar** plus , B** plus and BF//2** plus as the primary ions. At different implant dosages, simulated profiles, sheet resistances, I-V curves were measured to determine the properties of the implanted surface layers. It was found that the activation of the recoiled Al was much lower compared with that of B. At low implant dosages, Schottky barriers were formed. They became p-n junctions at the higher implant dosages. Transitional properties were affected by the recombination mechanisms and damage. The Ar** plus -implanted samples produced p-n junctions with somewhat inferior characteristics.