Out-diffusion of impurity via the kick-out mechanism during gettering

The out-diffusion of an impurity by the kick-out mechanism during gettering is analyzed by the numerical solution to the set of diffusion-kinetic equations. On the example of the Au impurity in silicon, the effect of the degree of gettering and the dislocation density on the concentration profiles of the impurity and self-interstitials is investigated. It is shown that the usually used approximation based on the solution to diffusion equations for a substitutional impurity with effective diffusivities can lead to an underestimation of the gettering time. In the absence of dislocations, this underestimation is caused by modifying the expression for effective diffusivity in the case of gettering and violating the local-equilibrium condition at the gettering front. For a high dislocation density, the process of lowering the impurity-concentration level is caused by the kinetics of generation of self-interstitials on dislocations instead of the impurity diffusion.