Identification of Silicon Interstitials in Ion Implanted GaAs

The lattice location and diffusion of silicon has been studied in $[100]$ GaAs implanted with 1×10¹⁶ 40-keV ³⁰Si⁺ions/cm². The identification of silicon interstitials was made by fitting a concentration dependent diffusion model to the annealed silicon depth profiles measured with secondary ion mass spectrometry. In the diffusion model presented, in addition to silicon located on Ga and As sites and SiGa⁺-SiAs^- pairs, interstitial silicon is also taken into account for the first time. The charge state of the silicon interstitial was calculated to be $+1$ in order to best fit the experimental profiles.