We zone-engineered HgCdTe/HgTe/HgCdTe quantum wells (QWs) using the molecular-beam epitaxy (MBE) method with in situ high-precision ellipsometric control of composition and thickness. The variations of ellipsometric parameters in the w-D plane were represented by smooth broken curves during HgTe QW growth with abrupt composition changes. The form of the spiral fragments and their extensions from fracture to fracture revealed the growing layer composition and its thickness. Single and multiple (up to 30) Cd x Hg 1Àx Te/HgTe/Cd x Hg 1Àx Te QWs with abrupt changes of composition were grown reproducibly on (013) GaAs substrates. HgTe thickness was in the range of 16 nm to 22 nm, with the central portion of Cd x Hg 1Àx Te spacers doped by In to a concentration of 10 14 cm À3 to 10 17 cm À3 . Based on this research, high-quality (013)-grown HgTe QW structures can be used for all-electric detection of radiation ellipticity in a wide spectral range, from far-infrared (terahertz radiation) to mid-infrared wavelengths. Detection was demonstrated for various low-power continuous-wave (CW) lasers and high-power THz pulsed laser systems.
The ellipsometry and RHEED study of high-quality MCT films grown on (1 12)-and (130) CdTe and GaAs by MBE was carried out. The dependence of the ellipsometric parameter w on MCT composition is evaluated. It was shown that such parameters as growth rate, the surface roughness, initial substrate temperature, and film composition may be measured by the in-situ ellipsometry. The appearance of surface roughness was observed in the initial stage of MCT growth under various compositions
Germanium nanocrystals in Ge02 films have been obtained with the use of two methods and have been studied. The first method of Ge nanocrystal formation is a film deposition from supersaturated GeO vapor with subsequent dissociation of metastable GeO on heterophase system Ge:Ge02. The second method is growth of anomalous thick native germanium oxide layers with chemical composition GeO(H2O) during catalytically enhanced Ge oxidation, x is close to 1 . The obtained films were studied with the use of photoluminescence, Raman scattering spectroscopy, highresolution electron microscopy. Strong photoluminescence signals were detected in Ge02 films with Ge nanocrystals at room temperature. "Blue-shift" of the photoluminescence maximum was observed with reducing of Ge nanocrystal size in anomalous thick native germanium oxide films. So, the correlation between reducing of the Ge nanoerystal sizes (estimated from position of Raman peaks) and photoluminescence "blue-shift" was observed. The Ge nanocrystals presence was confirmed by high-resolution electron microscopy data. The optical gap in Ge nanocrystals was calculated with taking into account quantum size effects and compared with the position of the experimental photoluminescence peaks. It can be concluded that a Ge nanocrystal in Ge02 matrix is a quantum dot of type I. It was shown, that "band gap engineering" approaches can lead to creation of Ge:Ge02 heterostructures with required properties. This heterostructures can be perspective for using in opto-electronics, for creation of elements of quasi-nonvolatile MOS memory using Ge nanocrystals as traps for electrons or holes, e.t.c.
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