Dresden 2009 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 16: III-V semiconductors II
HL 16.3: Talk
Tuesday, March 24, 2009, 10:00–10:15, POT 151
Stain dependent optical properties of AlN measured by means of VUV-spectroscopic Ellipsometry — •Christoph Werner1, Marcus Röppischer1, Christoph Cobet1, Carsten Buchheim2, Rüdiger Goldhahn2, Frank Brunner3, and Nobert Esser1 — 1ISAS - Institute for Analytical Sciences, Albert-Einstein-Str. 9, 12489 Berlin — 2TU - Ilmenau, Institut für Physik, Weimarer Straße 32 (Faradaybau), 98693 Ilmenau — 3Ferdinand-Braun-Institut für Höchstfrequenztechnik (FBH), Gustav-Kirchhoff-Str. 4, 12489 Berlin
The growth of hexagonal group-III nitrides on foreign substrates causes in-plane strain due to the different thermal expansion coefficients of substrate and layer. Optical properties of semiconductors are strongly influenced by internal strain and electric fields. These effects were investigated in the dielectric function of aluminium nitride samples grown on different substrates (sapphire and silicon carbide) in the photon energy range from 4 to 9.5eV. The region around the fundamental band gap at 6 eV is of particular interest for the strain analysis. On the base of excitonic transitions, we have studied the crystal field and strain dependent ordering of the valence bands and oscillator strength at the Γ-point. Further more, various strain contribution in the temperature related shift of excitonic transitions are also been observed. Our measurements will be discussed in comparison to calculations within the kp-theory, XRD measurements and former published data.