2.1 Diffusion

Diffusion is a mass transport phenomenon where in dependence of
temperature molecular dynamic local exchanges take place. In case of
unequal distributed concentrations the statistical average of molecular
movements strives for balance the inequality. This molecular dynamic
behavior leads to a macroscopic flux that can be described as a
material transport caused by the gradient of concentrations known as
Fick's first law.

where

where

The conservation of dopant atoms is expressed by a continuity equation and is known as Fick's second law

In case of low doping concentrations (*intrinsic diffusion*) the
measured diffusion profiles are well behaved and agree with Fick's
laws. But at high doping concentrations the diffusion profiles deviate
from the predictive calculations of Fick's laws [Sch91].

1998-12-11