Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 53: Optical properties
HL 53.7: Vortrag
Freitag, 29. Februar 2008, 12:00–12:15, EW 201
Ab initio study of strain influence on electronic and optical properties of ZnO — •André Schleife, Claudia Rödl, Frank Fuchs, and Friedhelm Bechstedt — Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität and European Theoretical Spectroscopy Facility (ETSF), Max-Wien-Platz 1, 07743 Jena, Germany
ZnO is a material which has been in the scientific focus for many decades. Recently, this strong interest was renewed because of two aspects: First, ZnO is a promising material for optoelectronic applications due to the availability of high-quality single crystals in combination with large exciton binding energies. Second, it is an interesting semiconductor, especially since p-doping seems to become possible.
We study the effect of biaxial strain on the electronic band structure and the optical transitions near the absorption edge by means of an ab initio approach. Starting from density functional theory in combination with a nonlocal exchange-correlation functional we compute quasiparticle energies within Hedins GW approximation to obtain a correct electronic band structure. Excitonic effects are considered by solving the Bethe-Salpeter equation. The corresponding Hamiltonian is constructed using a GGA+U starting point in combination with hybrid k-point meshes.
We calculate the positions of the Γ9, Γ7, Γ7 valence levels and the corresponding excitons. The results may explain the long-standing problem of the correct valence-band ordering in ZnO by residual strain. Furthermore, we are able to derive k·p parameters for this material.