We investigate the dependence of carrier lifetimes in radiation‐damaged, GaAs on proton implantation dose by means of time‐resolved reflectivity and photoconductivity experiments with subpicosecond resolution. The carrier lifetimes decrease with increasing implantation dose at low implantation levels whereas beyond the ‘‘amorphization dose’’ a saturation at 0.5 ps can be observed due to a saturation of the defect density.