Regensburg 2002 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 43: Si/Ge
HL 43.3: Vortrag
Freitag, 15. März 2002, 11:00–11:15, H14
The neutral Cd-vacancy complex in Si and Ge — •Nicolae Atodiresei1, Winfried Kromen1, Stefan Blügel2, and Kurt Schroeder1 — 1Institut für Festkörperforschung, Forschungszentrum Jülich — 2Universiät Osnabrück
We have calculated the electronic and geometrical structure of the neutral Cd-vacancy complex in Si and Ge. The calculations were made using the pseudopotential ab initio molecular-dynamics-method based on the density-functional theory (DFT) in the local density approximation (LDA). We use the projector-augmented-wave (PAW) method to describe the scattering properties of Cd in the energy range of the valence electrons, Si and Ge are described with soft Kleinman-Bylander pseudopotentials. - The Cd-vacancy complex was placed in a supercell containing 107 atoms with c3v-symmetry, and the optimal structure was determined by total energy and force minimization. It turns out that the stable configuration is the ’split vacancy’ (Cd in a middle of a bond between two vacant sites). The Si or Ge neighbor atoms are displaced inward from the ideal positions by around 5% of the bond length. The highly symmetric Cd-split-vacancy complex is compatible with the low electric field gradient experimentally found in Ge [H.Haesslein, R.Sielemann and Ch.Zistl, Phys. Rev. Lett. 80, 2626 (1998)]. The substitutional Cd at a nearest neighbor site of a vacancy has a higher energy and relaxes directly into the ’split vacancy’ configuration. - The PAW-method was tested for a great variety of bulk systems like Cd-metal, CdO and CdS (cubic and hexagonal forms). All tests show a good transferability of the generated projector potentials.