Nonthermal Effects of Photon Illumination on Surface Diffusion

Nonthermal influences of photon illumination on surface diffusion at high temperatures have been measured experimentally for the first time. Activation energies and preexponential factors for diffusion of germanium and indium on silicon change substantially in response to illumination by photons having energies greater than the substrate band gap. Results depend on doping type. Ionization of surface vacancies by photogenerated charge carriers seems to play a key role. The results have significant implications for aspects of microelectronics fabrication governed by surface mobility.