Diffusion in Crystalline Silicon and Germanium — the State-of-the-Art in Brief

Abstract

In silicon, self-interstitials and vacancies coexist under thermal-equilibrium conditions. Above about 1000°C self-diffusion is dominated by an interstitialcy mechanism, and (so-called hybrid) elements which occupy both interstitial and substitutional sites (e.g., Au and Pt) diffuse almost exclusively via the kick-out mechanism. In the diffusion of substitutional solutes, small atomic size and Group-III membership (e.g., of B) favour interstitialcy diffusion, whereas large atomic size and Group-V membership (e.g., of Sb) are advantageous for diffusion via vacancies. There are indications that the importance of vacancies for diffusion processes in Si increases at temperatures below 1000°C. In germanium both self-diffusion and substitutional-solute diffusion take place by means of vacancies; the hybrid Cu undergoes dissociative diffusion.