The interstitial fraction of diffusivity of common dopants in Si

The relative contributions of interstitials and vacancies to diffusion of a dopant A in silicon are specified by the interstitial fraction of diffusivity, f_A. Accurate knowledge of f_A is required for predictive simulations of Si processing during which the point defect population is perturbed, such as transient enhanced diffusion. While experimental determination of f_A is traditionally based on an underdetermined system of equations, we show here that it is actually possible to derive expressions that give meaningful bounds on f_A without any further assumptions but that of local equilibrium. By employing a pair of dopants under the same point-defect perturbance, and by utilizing perturbances very far from equilibrium, we obtain experimentally f_Sb≤0.012 and f_B≥0.98 at temperatures of ∼800°C which are the strictest bounds reported to date. Our results are in agreement with a theoretical expectation that a substitutional dopant in Si should either be a pure vacancy, or a pure interstitial(cy) diffuser.