Deep-level transient spectroscopy was used to study the energy levels which were introduced by Au diffusion in polycrystalline p-type Si. Diffusion annealing (900C, 6h) was carried out in an Ar flow after a Au layer had been deposited, by cathodic sputtering, onto one side of the sample. Diodes of Al-Si were created on the other side of the samples, in grains, and on grain boundaries. The results showed that Au atoms reached the other side of the sample (40nm). They were in substitutional sites, and gave rise to the well-known donor level (Ev + 0.35eV) in p-type Si. However, in the case of the diodes which covered the grain boundaries, an additional level was found at 0.43eV above the valence band. The enhanced diffusion of Au atoms through the grains was explained in terms of the kick-out mechanism. In the case of the grain boundaries, it was suggested that the additional level might result from the formation of Au-Fe or Au-defect complexes.

M.Pasquinelli: Journal de Physique III, 1992, 2[3], 303-11