Subpicosecond carrier lifetimes in radiation-damaged GaAs.

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 wheras beyond the "amorphization dose" a saturation at 0.5 ps can be observed due to a saturation of the defect density.