Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 39: Group IV (other than C): Si/Ge/SiC

HL 39.6: Talk

Thursday, March 15, 2018, 12:15–12:30, EW 015

electronic and optical properties of hexagonal germanium: influence of echange and correlation — •valerio armuzza, jürgen furthmüller, claudia rödl, friedhelm bechstedt, and silvana botti — Institut für Festkörpertheorie und Optik der Friedrich-Schiller-Universität, Jena, Jena, Germany

Using ab initio density functional calculations, we study the effect of several Exchange and Correlation (XC) potentials on geometry, electronic and optical properties of Cubic (C) and Lonsdaleite (L) Germanium (Ge), including spin-orbit interaction and d-electrons. Given the importance of Ge in semiconductor technology, this work is directed to the best approach comparing with the well-known experimental results for C-Ge. It is applied on the L-Ge polytype. We initially obtain the lattice parameters, cohesive energies and bulk moduli with the LDA, PBE, PBEsol and AM05 potentials, while, subsequently the energy band gaps, band structures, optical transitions and radiative lifetimes are calculated with the PBEsol, a hybrid XC-funcional (HSE06) and a meta-GGA functional (MBJLDA). The atomic geometry for PBEsol and AM05 are consistent with experimental results. Band gaps are slightly overstimated (underestimated) for HSE06 (MBJLDA) in C-Ge, while we have the opposite situation in L-Ge. The small lonsdaleite gap and the symmetry of the lowest conduction bands are explained in terms of folding of the diamond-structure bands.