Defect structure and recovery in hydrogen-implanted semi-insulating GaAs

A beam of low-energy positrons together with ion-beam techniques have been used to profile defect and hydrogen distributions and their annealing behavior after the room-temperature implantation of 3×{}10¹⁵ to 1×{}10¹⁷ 60-keV H⁺ cm^-2 in semi-insulating GaAs. A monovacancy overlayer is observed close to the surface at 0--330 nm after 1×{}10¹⁷ H⁺ cm^-2 implantation. The vacancies in the stopping range of the implanted H at 330--720 nm are seen only after the annealing at 200 ^∘{}C, probably due to a release of hydrogen from the vacancies. The total vacancy depth of 720 nm correlates well with the distribution of displaced atoms and with the energy deposited in the H implantation. Above 350 ^∘{}C, the monovacancies in the region of 0--350 nm start to disappear, whereas at the depth of 350--750 nm stable vacancy-hydrogen agglomerates are formed at 400 ^∘{}C. The redistribution of the implanted hydrogen at 0--350 nm was observed to be connected with the migration of complexes containing implantation-induced defects.