Berlin 2005 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
HL: Halbleiterphysik
HL 30: II-VI Halbleiter III
HL 30.4: Vortrag
Samstag, 5. März 2005, 15:45–16:00, TU P164
Temperature-dependency of the fundamental band-gap properties of (0001)ZnO thin films — •Nurdin Ashkenov, Rüdiger Schmidt-Grund, Daniel Fritsch, Wolfram Czakai, Mathias Schubert, Holger Hochmuth, Michael Lorenz und Marius Grundmann — Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
We report on the temperature dependencies of the fundamental band-to-band transition energies, amplitudes and broadenings of (0001)ZnO thin films grown on (0001)Al2O3 substrate by Pulsed Laser Deposition. Spectroscopic ellipsometry (SE) data are measured at temperatures between 300 K and 830 K, and are supplemented by the photoluminescence data between 4.4 K and 300 K. SE data are analyzed by using model dielectric function approaches augmented by excitonic contributions. The increase of the valence band splitting upon temperature is indicative for a change of the crystal-field-splitting parameter. For ZnO, the phonon dispersion must be considered appropriately in order to model the temperature dependence of the fundamental band-to-band transition energy. We obtain strong contributions due to optical phonons at elevated temperatures, whereas acoustic phonons dominate the electron-phonon coupling at low temperatures. The experimentally determined bandgap energies are compared with those calculated by the Empirical Pseudopotential Method.