Nonequilibrium experiments on self-diffusion in silicon at low temperatures using isotopically enriched structures

Abstract

Self-diffusion in silicon has been studied using epitaxially grown isotopically enriched structures under nonequilibrium concentrations of native point defects created by thermal oxidation and nitridation. Comparing identical anneals for phosphorus, antimony, and self-diffusion in Si, we obtain experimental evidence for a dual vacancy–interstitial mechanism of self-diffusion with the possibility of a small substitutional exchange component. We determine that in the temperature range 800–1100°C, the interstitial-mediated fraction of self-diffusion is confined between 0.50 and 0.62. The corresponding activation enthalpies are 4.68 and 4.86eV for the interstitial and vacancy mechanisms, respectively. Furthermore, both mechanisms exhibit large activation entropies. This constitutes direct experimental evidence of the remarkable similarity between the energetics of these native point defects in silicon.