A study has been made of room-temperature implantations of large doses of P, As, and Sb into Si substrates, followed by annealing in the temperature range 550°-600° C and of implantations of these species into Si substrates maintained at 600 C. Neutron activation combined with anodic oxidation and HF stripping techniques was used to determine the profiles of the implanted ions. Electrical evaluation of the implanted layers by Hall effect and sheet resistivity measurements in conjunction with anodic oxidation and HF stripping techniques yielded profiles of the net electrically active species. The profiles obtained for 600 C implantations are markedly orientation dependent since the crystalline nature of the Si lattice is maintained during the implantation. Most of the P, As, or Sb ions implanted at room temperature are electrically active after annealing at 550°-600°C, and the carrier mobility observed in the implanted layer approaches that observed in comparably doped bulk Si. Only a small fraction of the ions implanted at 600°C are electrically active and uncompensated, and the carrier mobility in these layers reflects the increased scattering due to charged compensating defects. © 1970, The Electrochemical Society, Inc. All rights reserved.