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HL: Halbleiterphysik

HL 25: Si / Ge

HL 25.3: Vortrag

Samstag, 5. März 2005, 11:15–11:30, TU P-N226

Vacancy complexes with oversized impurities in Si and Ge — •K. Schroeder, H. Höhler, N. Atodiresei, R. Zeller, and P. H. Dederichs — Institut für Festkörperforschung, FZJ, 52425 Jülich

We examine the electronic and geometrical structure of impurity-vacancy complexes in Si and Ge. Within the framework of density-functional theory we use two complementary ab initio methods, the pseudopotential-PW method and the all-electron KKR method, to investigate the structure of vacancy complexes with 11 different sp-impurities. For Sn in Si, we confirm the split configuration (Sn on the bond center and two half vacancies on neighboring sites), and obtain good agreement with EPR data of Watkins[1]. We find that all impurities of the 5sp and 6sp series in Si and Ge prefer the split-vacancy configuration, with an energy gain of 0.5 to 1 eV compared to the substitutional complex. On the other hand, impurities of the 3sp and 4sp series form (slightly distorted) substitutional complexes. An exception from this rule is Al, which forms a split complex in Si and a strongly distorted substitutional complex in Ge. We find a strong correlation of these data with the size of the isolated impurities, defined via the lattice relaxations of the nearest neighbors.

[1] G. D. Watkins, Phys. Rev. B 12, 4383 (1975)