Low-temperature growth of epitaxial layers of ZnSe1−xTex solid solutions

The layers of ZnSe_1−xTe_x (0 < x < 1.0) solid solutions have been grown by liquid-phase epitaxy in a closed tube at 620–680 °C. Zinc chloride served as a solvent. ZnTe and ZnSe crystals were used as sources and substrates with orienting surfaces (110) and (111) for ZnSe and (110) for ZnTe. The composition of the grown layer was specified by the relative content of the ZnSe and the ZnTe in the solution and was controlled by X-ray analysis. The position of the exciton bands in the photoluminescence spectra of ZnSe_1−xTe_x over the interval 0.3 < x < 1.0 is in agreement with the free exciton energies calculated for these compositions. Relatively low-ohmic (of about 10² Ω cm) epitaxial layers of ZnSe_1−xTe_x solid solutions were grown.     

Calculations of homogeneous region in Ga1−xAlxAs and GaAs1−xPx ternary solid solutions

Ternary solid solutions of A^IIIB^V compounds are considered as pseudobinary A(x)^IIIB(x)^v compounds, where the behaviour of A(x)^III and B(x)^v pseudoatoms is quite similar to A^III and B^v atoms in a binary A^IIIB^v crystal. Weak dependence of point defect contribution into Gibb's energy of A^IIIB^v crystal on its defect nature, random character of ternary solid solutions of A^IIIB^v compounds allow to use already for binary compounds developed formalism in the determination of component thermodynamic potentials of solid solution. Basing on literature data for the equilibrium solidus of AlAs the approximation for the temperature dependence of thermodynamic potential of an AB quasimolecule in A^IIIB^v crystal is revised. This result together with the well-known parameters for the equilibrium liquidus in Ga–P, Ga–As, and Al–As systems were used for calculations of the nonstoichiometric factor at the boundary of a homogeneous region in Ga_1−xAl_xAs and GaAs_1−xP_x ternary solid solutions. The results are compared with the known literature data.     

Dynamics of structural defects of LPE-grown Gax-In1−xP Layers

The structural properties of epitaxial Ga_xIn_1−xP, LPE-grown on 〈111〉-oriented GaAs-substrate, have been investigated. Two groups of samples have been distinguished with respect to the lattice parameters of the layers (a₁) and the substrate (a_s): group A with a₁ < a_s and Δa/a_s = (0.85 ÷ 2.98)%, and group B with a₁ > a_s and Δa/a_s = (0.11 ÷ 1.98)%. Group A is characterized by a structure, including orthogonal, and slanted at 60° towards the surface, linear dislocations, originating from mismatch ones. Group B is characterized by a segmented-surface structure. The optimum conditions for the growth of GaInP layers on GaAs substrates (initial temperature, saturation and composition of the melt, as well as cooling rate) are discussed on the basis of the data obtained.     

Magnetically induced rhombohedral distortion in the UxTh1−xSe and UxY1−xSe solid solutions

Solid solutions of U_xTh_1−xSe for x = 1.00 ÷ 0.80 and the solid solutions of U_xY_1−xSe for x = 1.00 ÷ 0.60 were studied by the X-ray diffraction over the temperature range 100 ÷ 200 K. In both systems rhombohedral distortions of the cubic rock-salt crystal structure was observed below the Curie temperatures. The temperature and composition dependences of the rhombohedral angle ω of the rhomboedral cell and the \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{c' - a'}}{{a'}} $\end{document} ratio were determined.     

Magnetic properties of the CrSxTe1−x (x = 0−0.2) solid solutions

On the basis of X-ray, magnetic and neutron diffraction measurements the range of solubility in the CrS_xTe_1−x (x = 0−0.2) system has been established and the magnetic phase diagram of the system has been plotted. The decrease of magnetization at low temperature and the additional reflections in the neutron diffraction patterns are associated with the formation of noncollinear magnetic structure which is characterized by the antiferromagnetic component of the magnetic moments. This component has the orthorhombic unit cell with \documentclass{article}\pagestyle{empty}\begin{document}$ a_M = \sqrt {3a_0 } $\end{document}, b_M = a₀, c_M = c₀. The character of the exchange interactions giving rise to this magnetic structure is discussed.     

Crystal growth and investigation of CuAlxGa1−xTe2 solid solutions

Alloys of the CuGaTe₂‐CuAlTe₂ system have been synthesized by the one‐temperature method and homogenized by annealing. It was established for the first time by X‐ray and DTA methods that a continuous row of solid solutions is formed in the system. Large block crystals of CuAl_xGa_1−xTe₂ solid solutions have been grown by the Bridgman method (horizontal version). Measurements of density, microhardness and thermal expansion have been carried out on the grown crystals. It has been established, that the density and thermal expansion coefficients are changed linearly with composition, microhardness has a maximum at x = 0.6. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure defects investigation of GaAs and AlxGa1−xAs epitaxial layers

The paper is concerned with the results of investigation of structure defects in gallium arsenide and Al_0.3Ga_0.7As epitaxial layers. It was found that structure defects in layers under investigation are responsible for the excess component of the Schottky diode's reverse current.     

Quantitative analysis of Bi1−xSbx

The chemical composition of Bi_1-xSb_x alloys is determined by means of square-wave polarography, density measurements, measurements of the electron backscatter coefficient, and electron probe microanalysis. These experimental methods are discussed with respect to their results. At 10 keV, the electron probe microanalysis allows the determination of any antimony concentration without corrections (c_Sb = k_Sb).     

Thermodynamic Calculation of the Alloy Composition of GaxIn1−xAs Grown in the Trichloride System Using Solid Sources

The dependence of the Ga_xIn_1−xAs alloy composition as a function of the experimental input variables is calculated for a growth system using AsCl₃ and solid GaAs and InAs sources. The results are similar to those earlier obtained for growth in the hydride system. Additional AsCl₃ introduced downstream the source regions shifts the alloy composition towards higher GaAs content.     

Investigation of GaAs—InyGa1−yPzAs1−z–InxGa1−x-As grading heterojunctions formation

The initial stages of growth of GaAs–InGaAsP_var–In_xGa_1−xAs heterostructures (x = 0.1 and 0.17) were investigated for the equilibrium-cooling method of LPE growth. Similar investigations were carried out for GaAs–InGaAsP_var–In_0.05Ga_0.95As heterocompositions, but for the step-cooling technique. The scheme of growing of In_0.17Ga_0.83As films of GaAs substrates with several intermediate buffler InGaAsP_var layers is represented. These heterostructures were shown to have less than 10⁶ cm⁻² dislocation density on the overall area of the film (> 2 cm²).     

Liquid phase epitaxial growth and characterization of thin In1−xGaxAsyP1–y layers lattice-matched to InP

Growth studies enabled the deposition of In_0.71Ga_0.29As_0.68P_0.32 single quantum well structures with InP or In_0.88Ga_0.12As_0.26P_0.74 confinement layers lattice-matched to (001) InP by liquid phase epitaxy (LPE). Well widths in the order of 50–100 Å have been achieved using a conventional step cooling technique. The physical characterization has demonstrated the capability of the employed method to produce multilayered heterostructures which display confined particle states; quantum mechanically induced blue-shifts of the low temperature PL-emission up to 125 meV were measured. A remarkable reduction of the FWHM values of the shifted PL peaks was attained by optimization of the growth conditions.     

Thermal expansion in the AgGa(S1−xSex)2 solid solutions from X-ray diffraction data

The lattice parameters a and c as well as the axial thermal expansion coefficients in the AgGa(S_1-xSe_x)₂ solid solutions with chalcopyrite-type structure were determined as a function of temperature in the range from 80 to 700 K and composition x using an X-ray powder diffractometry technique. It is found that the thermal expansion coefficients were anisotropic and for all the solid solutions the thermal expansion coefficients along the tetragonal c-axis were negative whereas those along the a-axis and the volume coefficients were positive. The directions in which the crystal thickness does not change as temperature varies, were found. The composition dependences of these coefficients were non-linear.     

Phase diagram and single crystal growth of the CuInSe2xS2(1−x) solid solutions

The phase diagram of the CuInSe₂-CuInS₂ system is plotted using DTA and the solidus and liquidus lines by the approximation of the theory of regular and ideal solutions are calculated. The single crystals of the CuInSe_2xS_2(1−x) solid solutions are first grown by chemical transport.     

Debye characteristic temperatures from X-ray diffraction data and some thermal properties for AgGa1−xInxS2 solid solutions

Investigations of the Debye characteristic temperature for the AgGa_1−xIn_xSe₂ solid solutions, calculation of some thermodynamic properties and analysis of its variation during substitution of Ga by In showed the increase of the molar volume, density, heat capacity, enthalpy, and decrease of the melting temperature, microhardness, thermal expansion coefficients, intrinsic energy with zero-point energy, this giving evidence for a decrease of the forces of the interatomic interaction.     

The influence of ambient gas atmosphere on the liquid and solid composition at liquid phase epitaxial growth of GaAs–Alx-Ga1−xAs layers

Epitaxial gallium arsenide and gallium aluminium arsenide layers were grown from gallium solution on chromium-doped semi-insulating gallium arsenide. The effect of residual water concentration in the ambient gas atmosphere on change of aluminium in Al_xGa_1−xAs was determined. It was shown that a water concentration less than 5 ppm is necessary to grow epitaxial layers with high reproducible XAlAs-content and low carrier concentration.     

X-ray study of debye-waller factors and debye characteristic temperatures in AgGa(S1−xSex)2 solid solutions

The Debye-Waller factors and Debye characteristic temperatures for two principal crystallographic directions in the AgGaS₂–AgGaSe₂ solid solutions with chalcopyrite structure were determined by an X-ray powder diffractometry technique as a function of composition and temperature in the range from 80 to 700 K. The anisotropy of both the dynamical characteristics is shown to exist and the character of anisotropy changes with composition. The composition dependences of the Debye-Waller factors and Debye temperatures are non-linear. From the experimental data some thermodynamic properties were calculated and the variation of all investigated dynamical characteristics during anion substitution was analyzed.     

Infrared optical properties of (CuGe2P3)1−x(6 Ge)x solid solutions

Infrared reflectivity spectra of (CuGe₂P₃)_1−x(6 Ge)_x mixed crystals with compositions in the range x = 0.07–0.33 are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. An analysis of the spectra reveals six vibrational modes. The composition dependence of the mode frequencies and of the free carrier concentration and mobility is given and compared with infrared optical data for CuGe₂P₃.