First-principles studies of small arsenic interstitial complexes in crystalline silicon

Abstract

We present a first-principles study of the structure and dynamics of small As-interstitial complexes (${\text{AsI}}_{2}$, ${\text{As}}_{2}{\text{I}}_{2}$, ${\text{AsI}}_{3}$, and ${\text{As}}_{2}{\text{I}}_{3}$) in crystalline Si. These complexes can be important components of stable As-interstitial clusters or play a key role in interstitial-mediated formation of As-vacancy clusters. Neutral ${\text{AsI}}_{2}$ and ${\text{As}}_{2}{\text{I}}_{2}$ are identified as fast-diffusing species that contribute to As transient enhanced diffusion. We demonstrate that the extended defect configuration ${\text{As}}_{2}{\text{I}}_{3}^{\text{ext}}$ is a stable configuration with a binding energy of 2.64 eV. ${\text{As}}_{2}{\text{I}}_{3}^{\text{ext}}$ can serve as a nucleation site and facilitate the formation of larger As-interstitial clusters in presence of excess Si interstitials and high As concentration. We also discuss the implications of our findings on As transient enhanced diffusion and clustering and highlight the role of small As-interstitial complexes in ultrashallow junction formation.