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HL: Halbleiterphysik
HL 27: Poster II: SiC (1-7), Ultrakurzzeitdynamik (8-15), Halbleiterlaser (16-20), GaN (21-38), III-V Halbleiter (39-56), Photovoltaik (57-64), Störstellen (65-68), Tern
äre Halbleiter (69-70)
HL 27.47: Poster
Wednesday, March 29, 2000, 14:00–19:00, A
The physics of semiconductors under pressure: a theoretical investigation of the Grüneisen parameters of tetrahedral semiconductors — •P. Pavone1, B. Steininger1, K. Gaál-Nagy1, S. Klotz2, and D. Strauch1 — 1Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg — 2Physique de Milieux Condensés, Université P&M Curie, F-75252 Paris, France
The pressure dependence of the phonon frequencies of a typical tetrahedral semiconductor presents characteristic anomalous features: The transverse acoustic modes show a flat dispersion near the zone boundary and the corresponding Grüneisen parameters became negative. As a further consequence, this results in a negative thermal expansion. In this work, we present a study of the pressure dependence of the phonon frequencies of the prototype tetrahedral semiconductors Si, Ge, GaAs, and GaSb. We report on ab initio calculations of the Grüneisen parameters of the considered semiconductors as well as inelastic neutron-scattering experiments performed on Ge and GaSb. The relevance of first-principles calculations in the analysis of experimental data is discussed. Finally, we investigate the connection between the pressure dependence of the phonon frequencies and the linear thermal expansion coefficient within the framework of the quasi-harmonic approximation.