No abstract available

No abstract available

No abstract available

[en] Published in summary form only

No abstract available

No abstract available

[en] We present a comparative study of InAs/AlAs periodical structures with InAs and AlAs quantum dots (QD's) using infrared and Raman spectroscopies. Raman spectra were measured in a backscattering geometry using a micro-Raman setup to directly determine the transverse optical (TO) and longitudinal optical (LO) resonance frequencies. Remarkable features observed in the Raman spectra correspond to LO and TO phonons localised in AlAs and InAs QD's. The observed phonon lines are shifted from their bulk values due to tensile and compressive strain in AlAs and InAs QD's. The experimental IR spectra reveal the only minima at the TO phonon frequency positions attributed to the Froehlich modes. IR spectra were calculated supposing that the QD structures are described by the effective dielectric function within Bruggeman approximation taking into account dielectric properties of matrix and QD's materials and the volume fraction of QD's. Resonance frequencies were taken from an analysis of Raman spectra. A good correspondence of the experimental and calculated IR spectra proves the validity of the approach used

No abstract available

[en] Published in summary form only

[en] Full text. As it was established in Noetzel, R. Phys. Rev. Lett. 67, 3812, 1991) by an analysis of the RHEED oscillations. the (311) A interface in the GaAs/Al As superlattices (SL's) is disturbed by periodic corrugations. In this work we present the Raman scattering spectra of the (GaAs)_n (Al As)_n SL's grown by MBE on the (311) Ga As substrates which testify to the corrugation of the (311) A surface. The back-scattering spectra measured at T=80 K were taken with the samples grown on the (311)A surfaces. The thicknesses of the layers were chosen so that the estimated coherence length of optical phonons parallel to the layers was less than the periodicity of the corrugation (Yu. A. Pusep and others, to be published in Phys. Rev. B.); thus, the expected corrugation will not be averaged by the high-index confined optical modes. The comparison between the (311)A and the reference (001)SL's grown simultaneously allowed us to detect the splitting between the optical phonons confined in the narrow and wide parts of the Ga As layers formed by the interface corrugation. The analysis of the observed splitting gives the hight of the corrugation of about 2-3 ML's which is in good accordance with the recent RHEED data (M. Wassermeier and others. Phys. Rev. B. 51, 14721, 1995). (author)