Diffusion in Si isotope multilayer structures was studied at between 850 and 1100C. The diffusion of all dopants and self-atoms at a given temperature was modelled with the same setting of all native point-defect related parameters. The evaluation of the relative contributions of charged native point defects to self-diffusion permitted the determination of the defect energy levels introduced, by native point-defects, into the Si band-gap. Making allowance for the fact that the band-gap and the energy levels changed with temperature, an energy-level diagram of the native-point defects was obtained that exhibited a reversed level ordering for the donor levels of the self-interstitials. In accord with the general state of knowledge, the diffusion of B was mainly mediated by self-interstitials whereas the properties of both vacancies and self-interstitials were important to the modelling of As and P diffusion. The simultaneous diffusion of P and Si required the existence of a singly positively charged interstitial P. It was the diffusion of this defect that strongly affected the shape of the P diffusion tail and not only the supersaturation of self-interstitials. Taking into account the mechanisms of dopant diffusion and the properties of native-point defects determined from the simultaneous diffusion experiments, permitted the accurate description of reported dopant profiles. Altogether, this provided generally consistent data for modelling dopant and self-diffusion in Si for various experimental conditions. A comparison of experimentally and theoretically determined activation enthalpies of self- and dopant diffusion exhibited excellent agreement for self-interstitial-mediated diffusion but significant differences for vacancy-mediated diffusion in Si. This disagreement either reflected a deficiency of first-principles calculations for the accurate prediction of the energy band-gap of Si, or indicated a continuing lack of understanding of the diffusion in Si.

Self- and Foreign-Atom Diffusion in Semiconductor Isotope Heterostructures II - Experimental Results for Silicon. H.Bracht, H.H.Silvestri, I.D.Sharp, E.E.Haller: Physical Review B, 2007, 75[3], 035211