As all of the following diffusion current models are using diffusivities, we first summarize available diffusion coefficients models. The diffusion coefficient D can modeled as follows:
(4.3-1) gives the diffusivity at intrinsic doping
conditions, where (4.3-2) is appropriate to model the diffusion in
silicon dioxide, based on a temperature dependent diffusivity. Equation
(4.3-3) refers to the extrinsic dopant diffusion, where different
charge states of dopants are encountered. The same diffusion coefficient is
also taken for multiply charged dopant/defect pairs. If the dopant diffusion
is driven by excess point defect concentrations, the diffusion coefficient
is extended as depicted by (4.3-4), where
and
are
weighting factors representing the interstitial and vacancy diffusion
mechanism, respectively.