Dose dependence and annealing behaviour of radiation-induced defects in 70 MeV56Fe implanted GaAs

Single-crystal semi-insulating GaAs substrates implanted with 70 MeV56Fe ions with fluences varying from 5x1012 to 1x1014 ions/cm2, have been investigated by optical transmission over photon energy range 0.1-1.4 eV. The density of radiation-induced defect states shows a considerable increase for the fluences above 5x1013 ions/cm2. Annealing studies of the sample having the fluence of 1x1014 ions/cm2 show that significant damage recovery occurs over the temperature range 100-500 deg. C with activation energy of annealing to be 0.19 eV. The mid gap defect states are annealed out more rapidly than the near band edge defect states during annealing up to 350 deg. C whereas the near band edge defect states are annealed out more rapidly than mid gap defect states during annealing between 350 deg. C and 600 deg. C