Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 45: Group-III-Nitrides: Optical Properties II
HL 45.11: Vortrag
Mittwoch, 24. März 2010, 17:15–17:30, H15
Impact of stress on the optical properties of AlN layers — •Georg Roßbach1, Pascal Schley1, Gerhard Gobsch1, Rüdiger Goldhahn1, Marcus Röppischer2, Christoph Werner2, Christoph Cobet2, Norbert Esser2, Armin Dadgar3, Matthias Wieneke3, and Alois Krost3 — 1Technische Universität Ilmenau, Institut für Physik, PF 100565, 98684 Ilmenau — 2Institute for Analytical Sciences (ISAS), 12489 Berlin — 3Otto-von-Guericke-Universität Magdeburg, Institut für Experimentelle Physik, 39106 Magdeburg
The reversed valence-band (VB) ordering of wurtzite AlN with respect to GaN causes a strong dependence of the free excitonic transition energies on stress and a strong polarization anisotropy around the absorption edge. Here, we show that spectroscopic ellipsometry (0.9-9.8eV) is a powerful tool to determine both the ordinary and the extraordinary part of the dielectric function around the band edge of C-plane AlN layers. The investigations of films experiencing either tensile or compressive in-plane stress due to the growth on different substrates (Si, SiC and sapphire) allows us to demonstrate experimentally the stress dependence and anisotropy. The energy spacing of the three VBs at the center of the Brillouin zone is obtained from the analysis. The extracted shifts in energy are compared with the results of strain-dependent k*p calculations yielding in addition experimental values for the deformation potentials. Temperature-dependent studies reveal a strong influence of exciton-phonon interaction on the absorption.