High-resolution deep-level transient spectroscopy studies of gold and platinum acceptor states in diluted SiGe alloys - art. no. 235309

High-resolution Laplace deep-level transient spectroscopy spectra for gold- or platinum-diffused SiGe samples show an alloy splitting that is associat ed with the alloy fluctuations in the proximity of the defect. For the case of the platinum acceptor state, the effect of the level splitting caused b y alloying in the first and also in the second shell of surrounding atoms c an be distinguished. For the case of the gold acceptor, only the effect fro m the first shell of atoms is observable but the manifestation of alloying in the second-nearest shell can be seen as line broadening. We have found t hat the electronic energy level is affected by alloying in the first-neares t neighborhood by a factor of 2-3 more than by alloying in the second-neare st shell. The absolute values of the energy differences obtained from the A rrhenius plots for different defect configurations agree with those inferre d from the peak separations observed in the spectra. A clear preference for gold and platinum to enter substitutional Si sites adjacent to Ge has been revealed. This may be interpreted in terms of an enthalpy lowering as a re sult of the fact that both metals are able to replace the host silicon atom more easily than the germanium atom in the substitutional position.