The Effect of Vacancies Grown into Silicon on Gold Diffusion

Abstract

ABSTRACTWe propose a generalized model for gold diffusion in silicon based on the effect of the high concentrations of vacancies and vacancy complexes in the as-grown silicon. The monovacancy profiles calculated using this model are identical to the substitutional gold profiles calculated using the kick-out model. We deposited Au on commercial float zone Si in a vacuum system after the Si had reached the diffusion temperature (1233 K) and had been annealed in various ways. Contrary to previously published reports, we find the electrically active Au with a nearly one-sided profile when the Au is deposited on samples which were preannealed in vacuum. We conclude that annealed silicon surfaces lack the imperfections needed to make them effective sources or sinks for vacancies or self-interstitials. We propose that this can cause a high degree of supersaturation in the as-grown silicon crystal since the point defects cannot annihilate at the surfaces to maintain equilibrium as the crystal is cooled.