An infra-red absorption spectroscopic investigation was made of the thermal diffusion of Al from monatomic Al layers which were embedded in a GaAs epitaxial film. After

annealing, the absorption peak of the 2-dimensionally localized vibrational modes at 358/cm (due to Al layers) decreased while the peak at 362/cm (due to isolated Al atoms) increased. The 362/cm peak height was compared with the fraction of isolated Al atoms, as calculated by assuming second-nearest neighbor hopping diffusion from a monatomic Al layer and into the GaAs matrix. It was thus deduced that the diffusion coefficient of Al in GaAs was equal to 2 x 10-19cm2/s at 700C. It was concluded that this was a simple and reliable method for the investigation of impurity diffusion in crystals.

H.Ono. N.Ikarashi, T.Baba: Applied Physics Letters, 1995, 66[5], 601-3