Using ionized Mg beams accelerated to energies from 130 to 500 eV, Mg doping was studied in molecular‐beam epitaxy of GaAs. The incorporation coefficient of Mg increases by a factor of about 100 when compared with the use of neutral Mg beams. Hole concentrations as high as about 1×1019cm−3have been achieved. Photoluminescence measurements suggest that the damage due to Mg‐ion bombardment is negligible when the ion accelerating voltage (Va) ≲130 V. For higherVa, the damage can be removed by postgrowth annealing.