Properties of Gold-Doped Silicon

Abstract

Measurements of the temperature dependence of resistivity and Hall coefficient in gold-doped silicon show an acceptor level at 0.54 ev from the conduction band and a donor level at 0.35 ev from the valence band. These levels appear in equal concentrations within experimental error. The location of these levels is supported by photoconductivity measurements. A search was made for other levels associated with gold centers but none were found. The distribution coefficient for gold in silicon is 2.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$. Gold was introduced into the crystals by growing from a gold-doped melt and by diffusion into single crystals at high temperatures. The concentrations of gold observed in solution after saturation at various temperatures is consistent with that expected from the distribution coefficient. Gold acts as a recombination center detectable at concentrations as low as ${10}^{12}$ per ${\mathrm{cm}}^{3}$. Because the acceptor level is so close to the center of the forbidden band, it is possible to shift the Fermi level below the middle with large ratios of gold to residual donors. The acceptor level is measured in $p$-type silicon as 0.62 ev from the valence band, giving a value of band gap consistent with previous measurements by other methods.