Site preference next to germanium atom of gold and platinum impurities in SiGe alloy

Abstract

The technique of Laplace transform deep level transient spectroscopy has been used to study the acceptor levels of platinum and gold diffused into dilute (0–5% Ge) SiGe alloys. The high-resolution spectra obtained display a fine structure that we interpret as the effect of alloy splitting in terms of the relative number of silicon and germanium atoms in the immediate proximity of the transition metal. We show that Ge atoms in the first and in the second shell of atoms surrounding the impurity perturb the electronic properties of the well-known Au and Pt acceptor defects. For both defects the spectral distributions indicate an overpopulation of Ge-perturbed sites as compared to randomly occupied sites. This can be quantitatively interpreted in terms of an enthalpy difference of ∼60meV between configurations with zero or one Ge in the first or second shell surrounding the impurity.