Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 91: Poster Session: Quantum dots and wires: preparation & characterization & optical properties & transport properties

HL 91.22: Poster

Thursday, March 14, 2013, 16:00–20:00, Poster A

Group-IV nanocrystals: Spin-orbit coupling and optical properties from first principles — •Sebastian Küfner, Lars Matthes, Jürgen Furthmüller, and Friedhelm Bechstedt — Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena

The electronic structure of materials significantly changes due to spatial confinement. Consequently, nanostructures are interesting objects for manipulating electronic and optical properties. We use density-functional theory within local density approximation to calculate the electronic structure of α−Sn, Ge, and Si nanocrystals (NCs). We investigate the spin-orbit splitting of the highest occupied state and show that its size dependence appears to be not monotonic in case of Ge and Sn. We identify the spin-orbit splitted states by the degree of degeneracy and the symmetry of the wave-functions. In addition, we show how the size dependence of the electronic structure influences the optical absorption- and emission properties of the nanodots. Calculating the oscillator strengths, we identify the transitions resulting in the main contributions to the absorption spectra. Applying the ΔSCF method which considers many-body effects and screened Coulomb interaction, we calculate the optical Stokes-shifts depending on the NC-diameter as the difference between the lowest electron-hole excitation and recombination energy. We also give values for the corresponding radiative lifetimes.