The non-thermal effects of illumination upon surface diffusion at high temperatures were measured. It was found that the activation energies and pre-exponential factors for the diffusion of Ge changed upon illumination with photons having energies that were greater than the substrate band-gap:

n-type substrate, non-illuminated:     D (cm2/s) = 4.0 x 102 exp[-2.44(eV)/kT]

n-type substrate, illuminated:     D (cm2/s) = 3.0 x 101 exp[-2.20(eV)/kT]

p-type substrate, non-illuminated:     D (cm2/s) = 4.0 x 102 exp[-2.44(eV)/kT]

p-type substrate, illuminated:     D (cm2/s) = 4.0 x 103 exp[-2.71(eV)/kT]

These parameters decreased for n-type material, and increased for p-type material.

R.Ditchfield, D.Llera-Rodríguez, E.G.Seebauer: Physical Review B, 2000, 62[20], 13710-20