G. G. Devyatykh Institute of Chemistry of High−Purity Substances of the Russian Academy of Sciences, Nizhny Novgorod:

T. V. Kotereva

A. V. Gusev

V. A. Gavva

E. A. Kozyrev

Results are reported on an investigation of IR−absorption spectra of shallow donors and acceptors in high−purity single crystals of stable ²⁸Si(99.99%), ²⁹Si(99.92%) and ³⁰Si(99,97%) silicon isotopes grown by zone melting. The content of residual boron, phosphorus and arsenic impurities has been determined in the single crystals with a detection limit of 1 · 10¹² at./cm³, 4 · 10¹¹ at./cm³ and 1 · 10¹² at./cm³, respectively. IR−spectroscopy results on the content of shallow donors and acceptors are in a good agreement with the data on concentration of uncompensated charge carriers obtained by Hall measurements. The parameters of absorption lines for the boron and phosphorus impurities in the single crystals of silicon isotopes have been studied. We show that a change in the isotopic composition of silicon leads to a shift in the energy spectrum of shallow impurity centers towards the high−energy range with an increase in the atomic mass of the isotope.

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