Mossbauer study of Fe in GaAs following 57Mn+ implantation

Mossbauer measurements have been performed on a GaAs single crystal sample following the implantation of radioactive Mn-57(+) (T-1/2 = 1.5 min) ions. The Mn+ ions were implanted with 60 keV energy into a GaAs sample held at temperatures of 300-700 K in an implantation chamber. Implantation fluences were <2 x 10(12) ions/cm(2) which assured single ion implantations. Mossbauer spectra were measured with a resonance detector equipped with Fe-57 enriched stainless steel foils mounted on a conventional drive system outside the implantation chamber. The spectra at the lower temperatures are dominated by an asymmetrically broadened quadrupole split doublet (Fe-D), assigned to Fe in implantation induced damaged surroundings; at higher temperatures a single line dominates, due to Fe at undisturbed substitutional sites (Fe-S). The spectra also required small contributions (approx. 13-5%) of a quadrupole split component, Fe-X, which may be due to interstitial Fe and Fe in vacancy complexes. A prominent annealing stage is evident in the temperature range 300-550 K, leading to substantial increase in the Fe-S fraction, and attributed to mobile Ga vacancies.