Regensburg 2016 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 27: Zinc Oxide and Zinc Selenide
HL 27.7: Vortrag
Dienstag, 8. März 2016, 11:30–11:45, H17
Inversion of absorption anisotropy in wurtzite MgZnO — •Maciej Neumann1, Martin Feneberg2, Rüdiger Goldhahn2, Jean-Michel Chauveau3, and Norbert Esser1 — 1Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., 12489 Berlin, Germany — 2Otto-von-Guericke-Universität Magdeburg, 39106 Magdeburg, Germany — 3University of Nice Sophia-Antipolis, 06103 Nice, France
ZnO and its ternary alloy MgZnO are considered promising candidates for optoelectronic devices operating in the violet and ultraviolet regime. Therefore, the precise knowledge of its optical properties is mandatory. They are characterized by the dielectric function (DF) perpendicular and parallel to the optical axis, respectively.
Using spectroscopic ellipsometry the DFs were obtained from m-plane MgZnO thin films with Mg contents up to 45 %, grown on ZnO substrates by plasma-assisted molecular beam epitaxy. With increasing Mg content the absorption edges of the DFs shift to higher energies, whereas the splitting between the perpendicular and the parallel DF decreases. This results in an inversion of the absorption anisotropy above approximately 24 % Mg content. In order to gain insight this behavior a line shape analysis of the DFs in the vicinity of the bandgap is performed. It considers free excitons, exciton-phonon complexes, and Coulomb enhanced interband transitions, yielding characteristic transitions energies. Using these transition energies the inversion is explained in terms of valence band ordering and oscillator strength.