CVD grown boron marker layers were used to monitor the release of silicon interstitials from an arsenic doped surface region that was subsequently implanted with silicon. These structures were annealed for various times at 750°C in a nitrogen ambient. A comparison of boron spike enhancement and defect dissolution is made. It is shown that enhancement values from the Si+ implant were reduced at short times for samples containing arsenic compared to samples implanted with Si+ alone or As− alone. The TEM results showed that defect densities were dramatically reduced for the samples containing As. These results imply that the previously reported reduction in {311} formation observed in As doped wells is most likely not a Fermi level effect and is consistent with the formation of As interstitial clusters (AsIC's). The data shows that AsIC's form and control extended defect formation and slow the enhanced diffusion.