xTe Solid Solutions Research Articles

Contribution of Mechanical Stresses to the Surface Relief Formation Under Laser Irradiation of Semiconductors

The paper considers the effect of elastic stresses arising under pulsed laser irradiation of epitaxial layers of CdxHg1–xTe solid solutions on the formation of a periodic surface relief as a result of recrystallization of material melted by radiation.

Structural Properties of Cd x Hg1–xTe Solid-Solution Nanoparticles

It is shown that Cd x Hg1–xTe solid-solution nanoparticles can be produced by ball milling, but their presence is masked by larger particles. The methods of laser-correlation spectroscopy and X-ray-diffraction analysis have been used to study the structure of the nanoparticles and their size distribution. The presence of a compositional disordering of the solid solution structure was experimentally confirmed.

Multifractal spectrums for volumes of spatial forms on surface of ZnxCd1−xTe–Si (111) heterostructures and estimation of the fractal surface energy

Multifractal (MF) analysis is used to describe volumes of spatial forms that are formed on the surface of thin layers of ZnxCd1−xTe solid solution grown on the Si (111) substrate. MF analysis is performed on the basis of AFM images of the solid solution surface. The parameters of the MF spectrums for the distribution of volumes of the spatial forms, which formed the surface relief, were found. On the basis of a formal approach and data on the multifractal parameters for the volume and the area of the surface spatial forms the mathematic expression which takes into account the contribution of the fractal surface structure in its surface energy were proposed. The behavior of the surface energy of the system depending on the fractal parameters that describe the volume and the area of the spatial forms on the fractal surface were discussed.

Investigation of phase transitions in a system of Cd–Hg–Te solid solutions in a powerful laser radiation field

The investigation is devoted to phase transitions initiated by pulsed laser radiation in CdxHg1–xTe solid solutions. Direct measurements show the formation of new phases and determine their composition.

Multifractal parameterization of space forms on surfaces of Zn x Cd1 − x Te-Si(111) heterocompositions and its relationship to the conditions of layer synthesis

Multifractal (MF) analysis of space forms on the surfaces of thin layers of Zn x Cd1 − x Te solid solution precipitated onto a Si(111) substrate via the hot wall approach is performed. AFM images of film surfaces are used for MF analysis. The parameters of MF spectra are determined for the film surfaces of the above system. It is shown that the MF functions of system correspond to their canonical forms, and the resulting computational procedure can be applied to describe and analyze the state of spatial fractal structures that form on a layer’s surface. The quantitative relationships between the parameters of the MF spectrum of a film’s surface and its conditions of precipitation are revealed.

Multifractal analysis of areas of spatial forms on surface of ZnxCd1−xTe–Si (111) heterocompositions

A multifractal (MF) method is used for analysis of areas of spatial forms on the surface of thin layers of ZnxCd1−xTe solid solution grown on the Si (111) substrate by a method of the hot-wall epitaxy. AFM images of the film surface are considered as input information for the MF analysis. The parameters of the MF spectra of the film surface are obtained. It is shown that the MF parameters correspond to their canonical forms, and the developed computational approach can be applied to describe and analyze the spatial fractal structures formed on a layer surface. The quantitative relationships between the MF spectrum parameters of a film surface and its growth conditions are found.

Thermally stimulated electromagnetic-field spectra in planar structures of complex composition: II. Radiative fields

It is demonstrated that a wealth of unambiguous information on the details of the atomiclattice dynamics of solidsolution films can be acquired from a spectral study of the resonance features of thermal fields in immediate proximity to the planarstructure surface. The calculated spectral densities of the pand spolarized states of the nonradiative componen t of thermal fields in a planelayered (or Cd xZn 1- xTe solid solution filmonmetal substrate) system are compared us ing the refraction additivity principle. The spectral densities are calculated for different impurity concentrations and thicknesses of the film and various distances from the structure surface.

Structural and electrical properties of ZnS/CdTe and ZnTe/CdTe heterostructures

We investigated the structural, substructural and electrical properties of ZnS/CdTe and ZnTe/CdTe heterostructures obtained by the close-spaced vacuum sublimation. It was found that the structural properties of CdTe and ZnTe thin films deposited on ZnS or CdTe sublayers are better than those of the films obtained on glass substrate at the same growth conditions. XRD-analysis has shown that ZnxCd1−xTe (x = 0.21–0.30) solid solutions having the cubic phase were formed near the films' interfaces. Furthermore, the saturation current, the ideality factor and the value of the potential barrier height were determined by the analysis of dark current–voltage characteristics. This makes it possible to establish optimal growth conditions of ZnS/CdTe heterojunctions.

Synthesis and X-ray diffraction of Cd x Hg1 − x Te solid solutions

The CdxHg1 − xTe solid solutions were synthesized by combining two methods: immersion of CdTe single crystals in liquid mercury and thermal homogenization in mercury vapors. The samples obtained were studied by X-ray diffraction and X-ray fluorescence analyses. Nonstoichiometric cadmium microinclusions were shown to present in the initial CdTe single crystals and the solid solutions synthesized. The samples annealed in mercury vapors have smaller unit cell volumes than unannealed samples.

Energy spectrum of charge carriers in Sm x Pb1 − x Te

The electrical conductivity (σ), Hall coefficient (RH, and thermopower (α) of SmxPb1 − xTe have been measured at temperatures from 80 to 800 K. The results demonstrate that the SmxPb1 − xTe solid solutions with x ≤ 0.04 are p-type semiconductors. We have determined the electron effective mass at the conduction band bottom (mn = (0.031 ± 0.001)m0) and Fermi level (m* = (0.06 ± 0.001)m0) and the hole effective mass (mp = (0.34 ± 0.001)m0). The temperature-dependent σ, RH, and α data are interpreted in terms of a model with two carrier types.

Impurity and phase compositions of the surface of Cd x Hg1−x Te solid solutions

The results of our studies of the real surface impurity and phase compositions of CdxHg1 − xTe solid solutions and changes in the compositions induced by thermal evacuation and ion bombardment are presented. The impurity and phase compositions of the surface of CdHgTe solid solutions exposed to air included the gases and vapors (CO, O2, H2O) and hydrocarbons adsorbed from the atmosphere. Thermal vacuum treatment of the samples at 615 K led to surface purification from organic impurities, oxygen, water, and mercury microinclusions. The CdxHg1 − xTe sample surface was completely cleaned and its stoichiometric composition achieved by ion etching to a depth of 100 A.

The kinetics of low-temperature liquid phase epitaxy in the Zn-Cd-Te system

The kinetic corrections for the supersaturation of the initial liquid phase providing the preparation of ZnxCd1 − xTe solid solution layers at low deposition temperatures (500–600°C) were found. The results of kinetic modeling were in satisfactory agreement with the experimental data. It was shown that the inclusion of corrections for supersaturation of the initial liquid phase to the data on phase equilibria in the Zn-Cd-Te system was necessary for finding the temperature-time conditions of the crystallization of layers with the required composition.

Etching of Zn x Cd1 − x Te by solutions of the HNO3-HBr-citric acid system

Chemical etching of CdTe single crystals and Zn xCd1−xTe solid solutions by bromine-evolving etchants of the HNO3-HBr-citric acid system is studied. Projections of the surfaces of equal dissolution rates are plotted; the kinetics of etching processes and the influence exerted on it by the composition of solid solutions and initial concentrations of citric acid are found. The concentration limits of solutions for chemicody-namical polishing of surfaces of the mentioned semiconductors are determined.

Investigation of Phase Transition in Stacked Ge-Chalcogenide/SnTe Phase-change Memory Films

ABSTRACTPhase transitions in stacked GeTe/SnTe and Ge2Se3/SnTe thin layers for potential phase-change memory applications have been investigated by X-ray diffraction using a two-dimensional area detector system. The as-deposited underlying GeTe or Ge2Se3 layer is amorphous, whereas the top SnTe layer is crystalline. In the GeTe/SnTe stack, the crystallization of GeTe phase occurs near 170°C, and upon further heating, the GeTe phase disappears, followed by the formation of rocksalt-structured GexSn1−xTe solid solution. In the Ge2Se3/SnTe stack, the phase transition starts with the separation of a SnSe phase due to the migration of Sn ions into the Ge2Se3 layer. SnSe is believed to facilitate the crystallization of Ge2Se3-SnTe solid solution at ∼360°C, which is much lower than the crystallization temperature of Ge2Se3, therefore consuming less power during the phase transition.

Etching behavior of CdTe and ZnxCd1−x Te single crystals in aqueous H2O2-HBr-lactic acid solutions

We have studied the etching behavior of single crystals of CdTe and ZnxCd1−x Te solid solutions in aqueous H2O2-HBr-lactic acid bromine-releasing solutions and the mechanism of the dissolution process. The results have been used to construct dissolution rate-composition diagrams (contours of constant dissolution rate) and locate the composition region of solutions suitable for the dynamic chemical polishing of these semiconductor materials.

Correlation of resonance scattering and superconductivity in Pb xSn 1− xTe solid solutions doped with In

The Hall coefficient and resistivity were measured on a series of samples of Pb x Sn 1− x Te with 0⩽ x⩽0.45 and 5 at% of InTe as a dopant. All samples show p-type conductivity with hole concentration in the range from 10 19 to 10 21 cm −3 at 77 K . A slight decrease of Hall mobility and corresponding increase in the scattering cross-section of holes by impurity atoms was observed with an extremum at x=0.25. All samples exhibit a transition to a superconducting state with the critical temperatures ranging from 0.3 to 3.0 K . The maximum of d H c2/d T (where H c2 is the second critical field) correlates with the fall in mobility (or rise in the scattering cross-section of holes), which shows that the resonance scattering mechanism is playing an important role in the enhancement of superconducting properties of these solid solution materials.

Numerical study for liquid phase epitaxy of Cd XHg 1− XTe solid solution

The paper presents a numerical study of natural convection in the liquid phase epitaxy of Cd X Hg 1− X Te solid solutions. The simulation is carried out in frame of 2D time-dependent model accounts for solutal convection in the Boussinesq approximation, the phase equilibrium and mass conservation at the liquid/solid interface. The effect of convective mass transfer on the growth dynamics of epitaxial layers, their composition, surface shape and composition uniformity along the growth direction and across the layer area have been studied over a wide range of experimental conditions.

Study of the effect of graded gap epilayers on the performance of CdxHg1−x Te photodiodes

The characteristics of the photodiodes based on CdxHg1−xTe solid solutions with graded gap layers were calculated in the context of a one-dimensional diffusion-drift model. The parameters of the photodiodes were shown to be improved when the p-n junction was located in the near-surface graded gap region rather than in the central homogeneous section of the structure. The photodiodes with the n-type layer adjacent to the substrate were found to offer an advantage over the diodes with the p-layer close to the substrate in the case of illumination from the substrate side.

Physico-chemical properties of Ga and In dopants during liquid phase epitaxy of CdxHg1−xTe

This work deals with the study by means of radioactive tracers and autoradiography, as well as measuring of galvanomagnetic properties, of Ga and In doping of epitaxial CdxHg1−xTe layers during their crystallization from a Te-rich melt. Ga and In were introduced in the form of Ga72 and In114 master alloys with Te. The effective distribution coefficients of Ga and In during the crystallization of the CdxHg1−xTe solid solutions with x=0.20 to 0.23 were determined by cooling the Te-base melt to 515–470°C. Depending on the concentration of the dopants and the time-temperature conditions of CdxHg1−xTe growth, these ratios for Ga and In were 1.5–2.0 and 1.0–1.5, respectively. The electrical activity of Ga and In was determined after annealing of the CdxHg1−xTe layers in saturated Hg vapor at 270–300°C. In doping of the epitaxial layers to (3–8)×1014 cm−3 with subsequent annealing in saturated Hg vapor at ∼270°C increases the carrier lifetime approximately by a factor of two as compared with the undoped material annealed under the same conditions.

Formation of homo- and hetero-interfaces in CdxHg1−xTe solid solutions by pulse laser irradiation

Comprehensive investigations were made of the photoconductivity, photomagnetic effect, magnetic field dependences of the Hall coefficient and of the relative conductivity in n- and p-type CdxHg1−xTe (CMT) solid solutions, which were irradiated with nanosecond ruby laser pulses. The samples were distinguished by both the structural and the component composition. Irradiation of CMT with subthreshold energy density modified the point-defect structure in the surface layer and improved homogeneity. An increase in the energy density shifted the maximum and the long-wavelength edge of the photoconductivity spectra toward shorter wavelengths and increased the photosensitivity of the epitaxial CMT layers with a cellular structure. Laser irradiation resulted in formation of an acceptor enriched layer in surface region of CMT samples. In the case of n-type crystals a conduction type inversion occurred and a built-in p-n junction arose; in p-type CMT epitaxial films p+-p junction arose under the action of nanosecond laser pulses.