Hall effect and sheet resistivity measurements combined with layer removal techniques indicated carrier concentrations for 20‐kV antimony implants into silicon that exceed the thermal equilibrium solubility. Annealing caused the carrier concentration to decrease toward solubility values. Supersaturation effects were not observed for gallium implants. For samples annealed at 800 to 900°C, the concentration of carriers increased linearly with implanted dose and leveled off at a value close to the thermal equilibrium solubility.