Defect structures created in implantations of radioactive Mn-57(+) ions into silicon-based semiconductors held at temperatures of 77-500 K have been studied by Mossbauer spectroscopy on the 14 keV gamma-radiation emitted in the decay of the 17 Fe daughter atoms. For implantations at <300 K, the majority of Fe atoms is located in a specific defect structure, likely within an "amorphous pocket", which anneals partially at 100-200 K and completely at 300-450 K. The latter is proven to occur within minutes by isothermal time delayed measurements and results in a substitutional incorporation of the Mn-57 probe atoms. The atomic structure of the annealing defect is compared to that of Fe in amorphous silicon upon Mn-57 implantation.