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

The technique of Laplace transform deep level transient spectroscopy has be en used to study the acceptor levels of platinum and gold diffused into dil ute (0-5% Ge) SiGe alloys. The high-resolution spectra obtained display a f ine structure that we interpret as the effect of alloy splitting in terms o f the relative number of silicon and germanium atoms in the immediate proxi mity 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 prop erties of the well-known Au and Pt acceptor defects. For both defects the s pectral distributions indicate an overpopulation of Ge-perturbed sites as c ompared to randomly occupied sites. This can be quantitatively interpreted in terms of an enthalpy difference of similar to 60 meV between configurati ons with zero or one Ge in the first or second shell surrounding the impuri ty. (C) 1999 Elsevier Science B.V. All rights reserved.