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HL: Fachverband Halbleiterphysik

HL 46: Poster 2

HL 46.8: Poster

Donnerstag, 29. März 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.