First-principles studies of di-arsenic interstitial and its implications for arsenic-interstitial diffusion in crystalline silicon

We propose new structural configurations and novel diffusion mechanisms for neutral di-arsenic interstitial (As2I2) in silicon with a first-principle density functional theory simulation within the generalized gradient approximation. With an assumption of excess silicon interstitials and high arsenic concentrations, neutral As2I2 is expected to be favorable and mobile with low-migration barrier. Moreover, because the diffusion barrier of arsenic interstitial pairs (AsI) is very low (< 0.2 eV) under the same conditions, As2I2 can be easily formed and likely intermediate stage of larger arsenic interstitial clusters.