Interaction of iron with the local environment in SiGe alloys investigated with Laplace transform deep level spectroscopy

Vl Kolkovsky, A. Mesli, L. Dobaczewski, N. V. Abrosimov, Z. R. Zytkiewicz, A. R. Peaker

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    Laplace transform deep level transient spectroscopy (LDLTS) is used to investigate the alloy effects on iron related deep centers in Si1-x Gex. A clear buildup of alloy disorder as a function of the germanium content has been observed for the isolated interstitial iron. However, due to specific features of the interstitial tetrahedral position of iron in the cubic lattice, it is not possible to say how many Ge atoms are responsible for the alloy-induced level splitting of the electronic state of the interstitial iron related defect. The observation of alloy splitting for the iron-boron pair has been used to resolve this issue. Different shells of nearest-neighbor atoms form the alloy pattern for both the interstitial isolated iron and the iron-boron pair. We show that for the iron-boron pair the occupied state is formed when a hole is closer to iron in the case of low germanium content. For more germanium rich alloy compositions the hole is bound by boron resulting in a dramatic change in the LDLTS peak structure. In an attempt to simulate the observed patterns, the alloying effects originating from different shells containing the defect were considered. A clear tendency for iron to form a pair with boron siting in germanium rich neighborhood is demonstrated. Finally, the influence of alloying on iron motion has been investigated. Similarities in the dissociation potential barrier heights of the iron-boron pair in pure silicon and Si0.98 Ge0.02 alloy suggest that the presence of Ge atoms induces only a second-order effect on the average diffusion barrier in alloys with low Ge content (less than 3%). © 2006 The American Physical Society.
    Original languageEnglish
    Article number195204
    JournalPhysical Review B - Condensed Matter and Materials Physics
    Issue number19
    Publication statusPublished - 2006


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