Diffusion and solubility of zinc in dislocation-free and plastically deformed silicon crystals

Floating-zone Si crystals enclosed in quartz ampoules were exposed to Zn vapour released by an elemental diffusion source. Penetration profiles of Zn in Si were recorded using the spreading-resistance technique or neutron activation analysis. Both the erfc-type distributions observed in plastically deformed specimens and the non-erfc profiles determined on dislocationfree wafers are consistently interpreted within the framework of the kick-out model. As an implication, Si self-interstitials generated in excess by interstitial-to-substitutional transitions of in-diffusing Zn atoms annihilate not only at the surface but also at dislocations. On the other hand, dislocation-induced segregation of Zn appears to be rather minor, as revealed by transition electron microscopy. Combining the Zn incorporation rate in dislocation-free Si with solubility data from saturated specimens yields the self-interstitial contribution to the Si self-diffusion coefficient.Dedicated to H.J. Queisser on the occasion of his 60th birthday