The role of vacancy on trapping interstitial O in heavily As-doped Si

We have investigated the interstitial oxygen (Oi) diffusion in heavily arsenic (As)-doped Si using first-principles calculations. We show that it is not the As per se but the Si vacancy (V) that trap Oi to reduce its diffusion. Arsenic actually plays the role of an arbitrator to activate thermal generation of As-V pairs, which in turn trap Oi with a large binding energy of ∼1.0 eV, in quantitative agreement with experiments. Our finding solves a long-standing puzzle on the atomistic mechanism underlying the retardation of Oi precipitation in heavily As-doped Si.