The non-thermal effects of illumination upon surface diffusion at high temperatures were measured (table 48). It was found that the activation energies and pre-exponential factors for the diffusion of Ge changed by up to 0.3eV, and by 2 orders of magnitude, respectively, upon illumination with photons having energies that were greater than the substrate band-gap. These parameters decreased for n-type material, and increased for p-type material. Together with photoreflectance spectroscopic data, this suggested that motion of the surface quasi-Fermi level for minority carriers accounted for much of the effect by changing the charge states of surface vacancies. An additional adatom-vacancy complexing mechanism appeared to operate on p-type substrates.

Semiconductor Surface Diffusion – Non-Thermal Effects of Photon Illumination R.Ditchfield, D.Llera-Rodríguez, E.G.Seebauer: Physical Review B, 2000, 62[20], 13710-20

Table 48

Arrhenius Parameters for Ge Diffusion on (111) Si Surfaces