Annealing kinetics of vacancy-related defects in low-dose MeV self-ion-implantedn-type silicon

Silicon samples of n-type have been implanted at room temperature with 5.6-MeV ${}^{28}\mathrm{Si}$ ions to a dose of $2\times {10}^8{\mathrm{cm}}^{\mathrm{-}2}$ and then annealed at temperatures from 100 to 380 °C. Both isothermal and isochronal treatments were performed and the annealing kinetics of the prominent divacancy ${(V}_2)$ and vacancy-oxygen (VO) centers were studied in detail using deep-level transient spectroscopy. The decrease of $V_2$ centers exhibits first-order kinetics in both Czochralski-grown (CZ) and float-zone (FZ) samples, and the data provide strong evidence for a process involving migration of $V_2$ and subsequent annihilation at trapping centers. The migration energy extracted for $V_2$ is ∼1.3 eV and from the shape of the concentration versus depth profiles, an effective diffusion length ⩽0.1 μm is obtained. The VO center displays a more complex annealing behavior where interaction with mobile hydrogen (H) plays a key role through the formation of VOH and ${\mathrm{VOH}}_2$ centers. Another contribution is migration of VO and trapping by interstitial oxygen atoms in the silicon lattice, giving rise to vacancy-dioxygen pairs. An activation energy of ∼1.8 eV is deduced for the migration of VO, in close resemblance with results from previous studies using electron-irradiated samples. A model for the annealing of VO, involving only three reactions, is put forward and shown to yield a close quantitative agreement with the experimental data for both CZ and FZ samples over the whole temperature range studied.