PACS 63.50.+x, 78.30.Fs We report results of Infrared and Raman spectra studies of bulk Zn 1-x Cd x Se. The obtained concentration dependences of oscillator parameters, reveals an unusual behavior. Besides two transverse optical (TO) and longitudinal optical (LO) branches, which are typical for a one-mode behavior, an additional branch getting into TO-LO splitting region was observed. We explained the nature of these "inserted modes" on the basis of the microscopic theory, which well describes the quasi-local mode frequency and the sign of splitting.

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The phonon modes of self-assembled Ge/Si quantum dots grown by molecular-beam epitaxy in an apparatus integrated with a chamber of the scanning tunneling microscope into a single high-vacuum system are investigated using Raman spectroscopy. It is revealed that the Ge-Ge and Si-Ge vibrational modes are considerably enhanced upon excitation of excitons between the valence band Λ 3 and the conduction band Λ 1 (the E 1 and E 1 + ∆ 1 transitions). This makes it possible to observe the Raman spectrum of very small amounts of germanium, such as one layer of quantum dots with a germanium layer thickness of ≈ 10 Å. The enhancement of these modes suggests a strong electron-phonon interaction of the vibrational modes with the E 1 and E 1 + ∆ 1 excitons in the quantum dot. It is demonstrated that the frequency of the Ge-Ge mode decreases by 10 cm -1 with a decrease in the thickness of the Ge layer from 10 to 6 Å due to the spatial-confinement effect. The optimum thickness of the Ge layer for which the size dispersion of quantum dots is minimum is determined.

We present a nondestructive method for quantitative determination of the vacancy concentration in the lattice of Hg-based semiconductor alloys with tetrahedral structure. The method is based on the identification of additional vibrational modes (AVMs) induced by lattice deformations in the far-infrared (FIR) reflectivity spectrum. Although the method is restricted by sensitivity limitations, recent FIR experimental data carried out on HgZnTe and HgCdTe samples containing Hg vacancies confirmed the presence of AVMs induced by Hg vacancies in as-grown crystals.

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