GaAs wafers were implanted with sulfur or silicon ions and annealed at temperatures from 800 to 950 °C under arsenic partial pressure controlled by arsine (AsH3) flow. Electrical characteristics obtained in this method were nearly identical or superior to those obtained with dielectric films. No sign of surface deterioration was observed even after annealing at 950 °C. The implantation into a Cr‐doped epitaxial layer resulted in better characteristics than into semi‐insulating substrates from a vender. The best doping efficiency of 89% was obtained with a dose of 1×1013Si+/cm2. The method is simple and reproducible, and suitable for the annealing process in production.