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

Abstract

Silicon samples of n-type have been implanted at room temperature with 5.6-MeV 28Si ions to a dose of 23108 cm22 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 (V2) and vacancy-oxygen ~VO! centers were studied in detail using deep-level transient spectroscopy. The decrease of V2 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 V2 and subsequent annihilation at trapping centers. The migration energy extracted for V2 is ;1.3 eV and from the shape of the concentration versus depth profiles, an effective diffusion length <0.1 mm 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 VOH2 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.