Yuji Ino

Mössbauer Spectroscopy on Fe Impurities in Si Materials

Based on a series of Mössbauer spectroscopic investigations on Fe impurities in p-type and n-type Si materials, we propose a new model for Fe impurities in Si matrix, consisting not only of interstitial Fe, but also substitutional Fe atoms with different charge states. Mössbauer spectroscopy enables us to observe directly these components which transform each other by changing external conditions such as under light illumination, under external voltage, and also under external stress. This means that not only interstitial Fe impurities, but also substitutional Fe impurities appear to be a source for producing “electrically active Fe impurities” in Si materials.

Direct Observations of Fe Impurities in Si with Different Fermi Levels by Mössbauer Spectroscopy

The charge states of Fe interstitial atoms in Si are investigated by Mössbauer spectroscopy. The spectra of 57Fe-diffused Si wafers are measured directly after the deposition at room temperature. The Fermi levels are changed by applying the external voltages to a Schottky junction, and by using different Si wafers with different dopant concentrations, providing different fractions of interstitial Feint0 and Feint+ Mössbauer components which correspond to the isomer shifts of 0.40 and 0.80 mm/s, respectively.