Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 46: Poster 2
HL 46.8: Poster
Thursday, March 29, 2007, 15:00–17:30, Poster A
Influence of anisotropic in-plane strain on the optical properties of (0001)-oriented GaN and ZnO films — •Marcus Röppischer1, Carsten Buchheim1, Rüdiger Goldhahn1, Gerhard Gobsch1, Florian Furtmayr2, Thomas Wassner2, and Martin Eickhoff2 — 1Technical University Ilmenau, Institute of Physics — 2Technical University Munich, Walter-Schottky Institute
The growth of hexagonal (0001)-oriented GaN films on a-plane sapphire substrates causes an anisotropic in-plane strain. It originates from the different lattice constants and thermal expansion coefficients of the substrate parallel and perpendicular to the c-axis. Under those conditions the optical response of the GaN films depends on the light polarization within the surface plane. We have applied photoreflectance spectroscopy in order to study the polarization dependence of the oscillator strength for the free A and B excitonic transitions. The experimental results are in good agreement with theoretical calculations based on the Bir-Pikus strain Hamiltonian and the experimentally determined lattice constants. Corresponding investigations of ZnO films reveal a much lower polarization anisotropy.