Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 92: Poster Session: II-VI Semiconductors & ZnO and related Materials
HL 92.13: Poster
Donnerstag, 29. März 2012, 16:00–19:00, Poster D
Anisotropic dielectric properties of MgZnO in the energy range from 2 to 25 eV — •Maciej D. Neumann1, Christoph Cobet1, Norbert Esser1, and Rüdiger Goldhahn2 — 1Leibniz-Institut für Analytische Wissenschaften – ISAS – e.V., 12489 Berlin, Germany — 2Otto-von-Guericke-Universität Magdeburg, 39106 Magdeburg, Germany
An accurate determination of the complex dielectric function (DF) of MgZnO is of great interest for the fundamental understanding of its electronic properties and is a key to optimize optoelectronic devices. Especially in the band gap region the DF is strongly affected by coulomb interaction and the polar character of the material. Even at room temperature this leads to characteristic features connected to free excitons and exciton-phonon complexes (EPC).
Using a home-made VUV ellipsometer at the Berlin synchrotron radiation facility BESSY II, nonpolar MgZnO samples were investigated with very high spectral resolution at temperatures between 10 and 300 K and photon energies ranging from 2 to 25 eV. We present the ordinary and extra ordinary DFs of the dielectric tensor obtained by employing an anisotropic model. The results are in remarkable agreement to novel ab-initio calculations and confirm the importance of excitonic effects in the entire VUV DF of MgZnO. The high resolution of around 0.5 meV allows us to extract all free band gap excitons (n=1 and n=2) and to elucidate the fine structure of the accompanying EPC.