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Cd-vacancy and Cd-interstitial complexes in Si and Ge

H. Hoehler·N. Atodiresei·K. Schroeder·R. Zeller·P. H. Dederichs
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Abstract

The electrical field gradient (EFG), measured e.g. in perturbed angular correlation (PAC) experiments, gives particularly useful information about the interaction of probe atoms like 111In / 111Cd with other defects. The interpretation of the EFG is, however, a difficult task. This paper aims at understanding the interaction of Cd impurities with vacancies and interstitials in Si and Ge, which represents a controversial issue. We apply two complementary ab initio methods in the framework of density functional theory (DFT), (i) the all electron Korringa-Kohn-Rostoker (KKR) Greenfunction method and (ii) the Pseudopotential-Plane-Wave (PPW) method, to search for the correct local geometry. Surprisingly we find that both in Si and Ge the substitutional Cd-vacancy complex is unstable and relaxes to a split-vacancy complex with the Cd on the bond-center site. This complex has a very small EFG, allowing a unique assignment of the small measured EFGs of 54MHz in Ge and 28MHz in Si. Also, for the Cd-selfinterstitial complex we obtain a highly symmetrical split configuration with large EFGs, being in reasonable agreement with experiments.

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H. Hoehler, N. Atodiresei, K. Schroeder, R. Zeller, P. H. Dederichs. 2004-06-24. Cd-vacancy and Cd-interstitial complexes in Si and Ge. https://doi.org/10.1103/physrevb.70.155313

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