Diffusion from an unlimited source

The surface concentration will be fixed at the solid solubility, and the distribution will be in the form of a complimentary error function:

where :

N = concentration (cm-3)

N 0 = solid solubility limit for dopant (cm-3)

x = position inside silicon relative to the surface

D = diffusion coefficient for dopant (cm2/s)

t = time (seconds)