DIFFUSION OF PLATINUM INTO DISLOCATED AND NON-DISLOCATED SILICON

Diffusion of Pt in Si was investigated with the aid of spreading-resis tance analysis using substrates of different dislocation density. Expe riments on virtually perfect, non-dislocated Si provide evidence for t he kick-out mechanism by the appearance of characteristic features in the concentration-depth profiles and by the diffusion-induced formatio n of stacking faults. In solar-grade Si, bulk incorporation of substit utional Pt is governed by the annihilation of self-interstitials at gr own-in dislocations having a density of about 10(9) m(-2). In this mat erial the efficiency of dislocations as self-interstitial sinks appear s to be reduced and dependent on penetration depth. Measurements on pl astically deformed Si with 10(11) to 10(13) dislocations/m(2) yield fo r the first time diffusion profiles that are determined by the transpo rt properties of interstitial Pt. The temperature dependence of the ov erall Pt diffusivity is characterized by an activation energy of 1.79 eV and a pre-exponential factor of 2.1 x 10(-4) m(2) s(-1).