Effect of silicon on relaxation of the crystal lattice in MOCVD–hydride Al<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>As:Si/GaAs(100) heterostructures

The X-ray diffraction and infrared spectroscopy data for MOCVD-hydride Al _x Ga_{1 − x} As:Si/GaAs(100) heterostructures and homoepitaxial GaAs:Si/GaAs(100) structures doped with Si to a content of up to ∼1 at % are reported. It is shown that, in the homoepitaxial heterostructures, the formation of alloys with Si yields a decrease in the crystal lattice parameters of the epitaxial layer and a negative lattice mismatch with the single-crystal substrate (Δa < 0). At the same time, the formation of quaternary alloys in the Al _x Ga_{1 − x} As:Si/GaAs(100) heterostructures is not accompanied by any pronounced strains in the crystal lattice. By introducing Si into the epitaxial layers of these heterostructures, it is possible to attain complete matching of crystal lattice parameters of the film and substrate in the appropriately chosen technological conditions of growth of the epitaxial layers.     

Specific features of the sol-gel formation and optical properties of 3d metal/porous silicon composites

The composition and optical properties of composite materials based on porous silicon with iron, cobalt, and nickel deposited by the sol-gel technique are studied. It is shown that the deposition of metal-oxide films onto the surface of porous silicon enables stabilization of the photoluminescence and an increase in its intensity, as well as the storage of hydrogen in the porous layer.     

A combined technique for studying the multicomponent spectra of photoreflection from semiconductors

A new technique for studying the multicomponent photoreflection spectra in semiconductors involves spectra measurements at different laser fluences and wavelengths in combination with spectrum phase analysis. To demonstrate the possibilities offered by the technique, the multicomponent photoreflection spectrum of the passivated homoepitaxial Si₃N₄/n-GaAs/n ⁺-GaAs wafer is analyzed.     

Generalized multilayer model for the quantitative analysis of the electromodulation components of the electroreflectance and photoreflectance spectra of semiconductors in the region of the E 0 fundamental transition

With the assumption of the Franz-Keldysh effect as the origination mechanism of the interband electromodulation E ₀ component, a generalized multilayer model of this effect was proposed. This model includes such physical parameters as the strength of the surface electric field and its decay profile in the space charge region, energy broadening, and partial modulation of the surface electric field. It was shown that the three regions can be defined in the simulated spectra, namely, the low-energy region, the region of main peak, and the high-energy region of the Franz-Keldysh oscillations. The effect of the model parameters on the line shape in these regions was studied. The ranges of the actual parameters were determined from the quantitative analysis of the experimental photoreflectance spectra of GaAs and InP substrates (n=10¹⁵ cm^?3–10¹⁸ cm^?3).     

Infrared reflectance spectra and morphologic features of the surface of epitaxial AlxGa1−x As/GaAs(100) heterostructures with the ordered AlGaAs2 phase

The infrared reflectance spectra associated with lattice vibrations in the epitaxial Al_xGa_1?x As/GaAs(100) heterostructures with different Al content in the cation sublattice are studied. The structures are grown by metal-organic chemical vapor deposition. In the spectrum of the structure with x ≈ 0.50, the vibration modes corresponding to the superstructurally ordered AlGaAs₂ phase are detected. The atomic force microscopy of the surface of the sample with x ≈ 0.50 reveals areas of ordered nano-scaled profile, with a period of ～ 115 nm. The ordered domains involve the AlGaAs₂ structured phase.     

Formation of silicon nanocrystals in multilayer nanoperiodic <Emphasis Type="Italic">a</Emphasis>-SiO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/insulator structures from the results of synchrotron investigations

The problem of the efficiency of the controllable formation of arrays of silicon nanoparticles is studied on the basis of detailed investigations of the electronic structure of multilayer nanoperiodic a-SiO _x /SiO₂, a-SiO _x /Аl₂О₃, and a-SiO _x /ZrO₂ compounds. Using synchrotron radiation and the X-ray absorption near edge structure (XANES) spectroscopy technique, a modification is revealed for the investigated structures under the effect of high-temperature annealing at the highest temperature of 1100°C; this modification is attributed to the formation of silicon nanocrystals in the layers of photoluminescent multilayer structures.     

Composition and optical properties of amorphous <Emphasis Type="Italic">a</Emphasis>-SiO<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript>:H films with silicon nanoclusters

The phase composition and optical properties of hydrogenated amorphous films of silicon suboxide (a-SiO_x:H) with silicon nanoclusters are studied. Ultrasoft X-ray emission spectroscopy show that silicon- suboxide films with various oxidation states and various amorphous silicon-cluster contents can be grown using dc discharge modulation. In films with an ncl-Si content of ～50%, the optical-absorption edge is observed, whose extrapolation yields an optical band gap estimate of ～3.2–3.3 eV. In the visible region, rather intense photoluminescence bands are observed, whose peak positions indicate the formation of silicon nanoclusters 2.5–4.7 nm in size in these films, depending on the film composition.     

Vegard’s law and superstructural phases in Al<Subscript>x</Subscript>Ga<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>As/GaAs(100) epitaxial heterostructures

The lattice constants of Al_xGa_1?x As epitaxial alloys with various AlAs (x) contents are determined for AlxGa_1?xAs/GaAs(100) heterostructures grown by MOC-hydride epitaxy using X-ray diffractometry and an X-ray back-reflection method. An ordered AlGaAs₂ (superstructural) phase is found in epitaxial heterostructures with x ≈ 0.50. The lattice constant of this phase is smaller than the lattice constants of an Al_0.50Ga_0.50As alloy and GaAs single-crystal substrate.     

Peculiarities of electron-energy structure of surface layers of porous silicon formed on p-type substrates

The atomic and electron structure of porous silicon surface layers were investigated by the methods of ultrasoft X-ray emission spectroscopy and X-ray absorption near edge structure spectroscopy. The thicknesses of the surface oxide layer and the degree of distortion of the silicon-oxygen tetrahedron in this layer were estimated. The thickness of the surface oxide layer lying on the amorphous layer, which covers the nanocrystals of porous silicon upon keeping for a year, exceeds severalfold the thickness of the natural oxidation of plates of monocrystalline silicon. The distortions of the silicon-oxygen tetrahedron??the main structural unit of silicon oxide??are accompanied by the strain of Si-O bonds and the increase in Si-O-Si bond angles.     

Structural and spectral features of MOCVD Al x Ga y In1 ? x ? y As z P1 ? z /GaAs (100) alloys

The study is concerned with MOCVD epitaxial heterostructures grown on the basis of Al _x Ga _y In_{1 ? x ? y} As _z P_{1 ? z} quinary alloys in the region of alloy compositions isoperiodic to GaAs. By the X-ray diffraction technique and atomic force microscopy, it is shown that, on the surface of the heterostructures, there are nanometric objects capable of lining up along a certain direction. From calculations of the crystal lattice parameters with consideration for internal strains, it can be inferred that the new compound is a phase based on the Al _x Ga _y In_{1 ? x ? y} As _z P_{1 ? z} alloy.