Dresden 2003 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 29: GaN: Pr
äparation und Charakterisierung II
HL 29.7: Vortrag
Mittwoch, 26. März 2003, 16:00–16:15, BEY/118
Phonons, band gap, and higher-energy interband transitions of hexagonal InGaN — •A. Kasic1, M. Schubert1, J. Off2, F. Scholz2, M. R. Correia3, S. Pereira3, Y. Saito4, M. Kurouchi4, and Y. Nanishi4 — 1Universität Leipzig, Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig — 2Universität Stuttgart, 4. Physikalisches Institut, Pfaffenwaldring 57, 70569 Stuttgart — 3Universidade de Aveiro, Dep. Fisica, Aveiro, Portugal — 4Ritsumeikan University, Faculty of Science and Engineering, Kusatsu, Japan
We report on phonon modes, band gap energy, and higher-energy interband transitions of differently strained InGaN films, for both low and high In contents. Employing spectroscopic ellipsometry (SE) in the mid-infrared range, the influences of strain and composition on the E1(TO) phonon mode frequency are separated and quantified. The SE results for the A1(LO) phonon mode are compared to those obtained from near-resonant Raman scattering studies. The Raman signal related to the A1(LO) mode depends considerably on the excitation energy.
The composition dependence of the band gap energy is obtained and discussed in view of the recent findings of other groups. Upon correction for a strong Burstein-Moss shift, the band gap of high-quality InN is determined as 0.78 eV. SE spectra in the vacuum-ultraviolet range revealed the E1 and E2 interband transitions, which shift to lower energies with increasing In content.