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×${10}^{15}$ to 1×${10}^{17}$ 60-keV ${\mathrm{H}}^{+}$ ${\mathrm{cm}}^{\mathrm{-}2}$ in semi-insulating GaAs. A monovacancy overlayer is observed close to the surface at 0–330 nm after 1×${10}^{17}$ ${\mathrm{H}}^{+}$ ${\mathrm{cm}}^{\mathrm{-}2}$ 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.