Berlin 2005 – wissenschaftliches Programm
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DS: Dünne Schichten
DS 24: Postersitzung II
DS 24.3: Poster
Dienstag, 8. März 2005, 17:00–19:00, Poster TU B
Anharmonic decay of optical phonons in III-V semiconductors at temperatures up to 1200 K — •Eugen Speiser1, Torsten Schmidtling2, and Wolfgang Richter1,2 — 1Department of Physics, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Rome, Italy — 2Institut für Festkörperphysik TU Berlin, PN 6-1, Hardenbergst. 36, 10623 Berlin, Germany
The anharmonic decay of optical phonons into lower frequency phonons is a fundamental process for energy relaxation in semiconductors. It manifests itself in the phonon linewidth which can be obtained from Raman scattering experiments. By measuring then the temperature dependence of the Raman linewidth the contribution of different decays processes can be tested. This has been done until now only for some elemental semiconductors. Comparable high temperature experiments on compound semiconductors have been rarely reported until now since their surfaces decompose and deteriorate easily at high temperatures. This surface deterioration leading to wrong results can be avoided by providing stabilisation of the volatile surface component by epitaxial stabilisation.
We have therefore combined a MOVPE(Metal Organic Vapour Phase Epitaxy) apparatus for III-V semiconductor growth with a Raman setup via a glasfibre to guide the inelastic scattered light from the sample inside reactor to the Raman spectrometer. We report first studies of the crystal anharmonicity done by Raman spectroscopy on stabilised GaAs and InAs surfaces at high temperatures. We will compare these results with literature data on the atomic mean square displacements obtained by x-ray diffraction.