Regensburg 2000 – scientific programme

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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 27.45: Poster

Wednesday, March 29, 2000, 14:00–19:00, A

Raman study of self-organized GaAs and AlAs islands embedded in InAs — •D. A. Tenne¹, V. A. Haisler¹, A. I. Toropov¹, A. K. Bakarov¹, A. K. Gutakovsky¹, A. P. Shebanin¹, and D. R. T. Zahn² — ¹Institute of Semiconductor Physics, 630090 Novosibirsk, Russia — ²Institut für Physik, Technische Universität Chemnitz, D-09107 Chemnitz, Germany

Vibrational spectra of self-organized GaAs and AlAs islands grown by molecular beam epitaxy on InAs (001) substrates were studied by Raman spectroscopy. We observed large strain-induced shifts of optical phonon frequencies of GaAs and AlAs islands with respect to the bulk materials. The values of shifts are 36 and 24 cm⁻¹ for GaAs LO and TO phonons; 55 and 28 cm⁻¹ for AlAs LO and TO phonons, respectively. Calculations of optical phonon frequencies in strained islands of different shape show that the observed shifts are characteristic for coherently strained islands, i. e. they do not contain dislocations that could lead to strain relaxation. Features of interface phonons were also observed in the Raman spectra between the peaks of InAs TO and LO phonons. The frequency positions of interface phonon lines are well described by the dielectric continuum model and also give evidence of three-dimensional island formation. Doublets of folded acoustic phonons are present in the low-frequency Raman spectra of multilayer structures with GaAs and AlAs islands. The frequencies of these doublet peaks agree well with elastic continuum model calculations and correspond to the folded acoustic phonons of superlattices with the same period. This shows that three-dimensional island formation does not significantly affect the low-frequency acoustic phonons.