Generation of dislocations in the CdTe/CdHgTe variband heterosystem at the initial stages of epitaxial growth

Microscopic studies, composition analyses, and studies of microhardness have shown that the epitaxial CdTe/CdHgTe variband heterosystem contains a developed system of dislocation ensembles of various nature (in-grown, mismatching, generated on the joint boundaries of three-dimensional islands, etc.) with segments inclined or parallel to the interface. It has been established that there is a correlation between an increase (inhomogeneous through the thickness) in the microhardness of the heterosystem and the distribution of the dislocation density in the epitaxial layer.     

Doping mechanisms of gallium arsenide with tin in gas phase epitaxy processes

A thermodynamic calculation of the equilibrium composition of the gas phase Ga-As-Sn-Cl-H system was carried out. An estimate of the impurity composition of adsorbate layers was made. A study of the electrophysical and photoluminescent properties of tin-doped GaAs epitaxial layers was conducted. From a comparison of the calculated and experimental data, it follows that the dependence of trapping mechanisms for tin on the conditions of epitaxial growth corresponds to changes in the gas phase and adsorbate layer compositions. A mechanism is proposed in which the introduction of impurities into the layers in elemental and complex forms occurs due to capture of atomic and diatomic tin adsorbed on the surface.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 37–40, June, 1990.     

Structure and properties of epitaxial layers of InxGa1−xAs grown from the gas phase

A study has been made of the dependence of the crystal lattice parameter and the structural perfection of epitaxial layers of In_xGa_1–xAs on substrates of GaAs and InP and on the composition of the solid solution. The electrophysical properties of layers of various compositions have been studied. From measurements of the photoluminescence spectra, a determination has been made of the dependence of the width of the forbidden band on the composition of the layers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 46–50, February, 1992.     

A change in the electro-physical properties of narrow-band CdHgTe solid solutions acted upon by a volume discharge induced by an avalanche electron beam in the air at atmospheric pressure

The effect of a nanosecond volume discharge forming in an inhomogeneous electrical field at atmospheric pressure on the CdHgTe (MCT) epitaxial films of the p-type conduction with the hole concentration 2·10¹⁶ cm³ and mobility 500 cm²·V^–1·s^–1 is studied. The measurement of the electrophysical parameters of the MCT specimens upon irradiation shows that a layer exhibiting the n-type conduction is formed in the near-surface region of the epitaxial films. After 600 pulses and more, the thickness and the parameters of the layer are such that the measured field dependence of the Hall coefficient corresponds to the material of the n-type conduction. Analysis of the preliminary results reveals that the foregoing nanosecond volume discharge in the air at atmospheric pressure is promising for modification of electro-physical MCT properties.     

The influence of AlN/GaN superlattice intermediate layer on the properties of GaN grown on Si（111） substrates

AlN/GaN superlattice buffer is inserted between GaN epitaxial layer and Si substrate before epitaxial growth of GaN layer. High-quality and crack-free GaN epitaxial layers can be obtained by inserting AlN/GaN superlattice buffer layer. The influence of AlN/GaN superlattice buffer layer on the properties of GaN films are investigated in this paper. One of the important roles of the superlattice is to release tensile strain between Si substrate and epilayer. Raman spectra show a substantial decrease of in-plane tensile strain in GaN layers by using AlN/GaN superlattice buffer layer. Moreover, TEM cross-sectional images show that the densities of both screw and edge dislocations are significantly reduced. The GaN films grown on Si with the superlattice buffer also have better surface morphology and optical properties.     

Growth of callium arsenide under various initial supersaturations in a Ga-AsCl3-H2 gas-transport system

A study has been made of the dependence of the electrophysical properties of layers on the molar concentration of AsCl₃ at the input of gas-transport system. It is shown that with an increase in the initial supersaturation, the impurity concentration in the films decreases and the carrier mobility increases. The observed changes in the layer parameters with the growth of the supersaturation is due to the combined effect of thermodynamic and kinetic factors.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 23–27, May, 1978.In conclusion, the authors thank M. P. Ruzaikin for his assistance in discussing the experimental results.     

Effect of the stresses caused by substrate on the electrical conductivity of ferromagnetic manganite lanthanum–barium films

This is a complex study of the electrophysical and magnetic characteristics of epitaxial manganite La_0.7Ba_0.3MnO₃ (LBMO) films under conditions of crystal structure stresses caused by misfit in the lattice parameters of the LBMO crystal and a substrate. The substrate used had the lattice parameter smaller than that in the LBMO crystal. It is shown that the temperature dependence of the electrical resistance of the films at low temperatures is not dependent on the existence of stresses in the film and agrees well with the calculation with allowance made for the interaction of carriers with magnetic excitations in the presence of strongly correlated electronic states. The study of the ferromagnetic resonance line indicates an inhomogeneity of the ferromagnetic phase in the LBMO films and the increase in the ferromagnetic resonance line width with decreasing temperature.     

Growth and impurity-trapping kinetics in sulfur-doped gallium arsenide epitaxy

Measurements have been made on the effects of crystallization conditions on the growth rates and electrophysical parameters for sulfur-doped epitaxial gallium arsenide films: gas speed, supersaturation, and deposition temperature. There is a correlation between the impurity concentration and the growth rate. The results are discussed from a model that incorporates interaction between impurity atoms and matrix ones.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 71–76, January, 1988.     

国产SiC衬底上利用AIN缓冲层生长高质量GaN外延薄膜

采用高温AlN作为缓冲层在国产SiC衬底上利用金属有机物化学气相外延技术生长GaN外延薄膜.通过优化AlN缓冲层的生长参数得到了高质量的GaN外延薄膜,其对称(0002)面和非对称(1012)面X射线衍射摇摆曲线的半峰宽分别达到130 arcsec和252 arcsec,这是目前报道的在国产SiC衬底上生长GaN最好的...     

MBE-grown Si: Er light-emitting structures: Effect of epitaxial growth conditions on impurity concentration and photoluminescence

The technology and properties of light-emitting structures based on silicon layers doped by erbium during epitaxial MBE growth are studied. The epitaxial layer forming on substrates prepared from Czochralski-grown silicon becomes doped by oxygen and carbon impurities in the process. This permits simplification of the Si: Er layer doping by luminescence-activating impurities, thus eliminating the need to make a special capillary for introducing them into the growth chamber from the vapor phase. The photoluminescence spectra of all the structures studied at 78 K are dominated by an Er-containing center whose emission line peaks at 1.542 μm. The intensity of this line measured as a function of the substrate and erbium dopant source temperatures over the ranges 400–700°C and 740–800°C, respectively, exhibits maxima. The edge luminescence and the P line observed in the PL spectra are excited predominantly in the substrate. The erbium atom concentration in the epitaxial layers grown at a substrate temperature of 600°C was studied by Rutherford proton backscattering and exhibits an exponential dependence on the erbium source temperature with an activation energy of ～2.2 eV.     

Angular dependence of the in-plane magnetization of (100) Cu/Ni/Cu structures

(100) Cu/Ni/Cu sandwich structures have been deposited on (100) Si using the (100) Cu epitaxially grown as the seed layer. The in-plane epitaxial relation between the metal films and Si allows the study of angular dependence of the magnetization for the field parallel to the film plane. Keeping the Cu layers at 1000 Å each and varying the Ni layers between 50 and 1000 Å, the magnetization along the [110] edge is larger than that along the [100] one. This is observed for both structures with a Ni thickness of 1000 and 500 Å, respectively. For the thinner Ni layers, the angular dependence is interfered by the reversal in magnetic anisotropy reported earlier. For such structures, a squared hysteresis loop is observed for the field perpendicular to the film plane, whereas one with little loop is observed for the in-plane magnetization. The angular dependence observed for the 1000 and 500 Å Ni films is the same as that of single crystal Ni. The (100) Cu/Ni/Cu films thus grown can be used for other magnetic measurements in the exploration of two-dimensional magnetism with controlled orientations.     

Fabrication of Ge-channel MOSFETs by using replacement gate process and selective epitaxial growth

We fabricated Ge-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) by using replacement gate process and selective epitaxial growth. In our method, thin Ge layers were selectively grown on the channel region of MOSFETs after the removal of a sacrificial gate stack structure and the etching of the channel region. Ge layers with a smooth surface and a good morphology could be obtained by using the thin Si_0.5Ge_0.5 buffer layer. Dislocations were observed in the epitaxial layers and near the interface between the epitaxial layer and the substrates. We consider that these dislocations degrade the device performance. Although the electrical characteristics of the obtained MOSFETs need further improvement, our method is one of the promising candidates for the practical fabrication process of Ge-channel MOSFETs.     

Photoluminescence spectra of Sn doped GaAs epitaxial layers: Influence of epitaxial process parameters

Photoluminescence measurements are performed with Sn doped GaAs epitaxial layers $\text{(}\text{n}\text{?}\text{= 4.10}{}^{18}$ to 1.1.10¹⁹ cm^?3) grown from a Sn solution. These samples exhibit the near-bandgap band and four further bands at 1.47, 1.33, 1.2 and 1.08 eV (77K). Their dependence on several parameters of the epitaxial process is studied systematically. The ratio of the peak intensities at 1.33 and 1.47 eV is observed to be influenced by the end temperature, by the growth rate of the layers, and by annealing processes. Comparison is made between the photoluminescence data and the doping concentrations which depend on the same parameters.     

Defect structure of epitaxial layers of III nitrides as determined by analyzing the shape of X-ray diffraction peaks

The shape of X-ray diffraction epitaxial layers with high dislocation densities has been studied experimentally. Measurements with an X-ray diffractometer were performed in double- and triple-crystal setups with both CuK _α and MoK _α radiation. Epitaxial layers (GaN, AlN, AlGaN, ZnO, etc.) with different degrees of structural perfection grown by various methods on sapphire, silicon, and silicon carbide substrates have been examined. The layer thickness varied in the range of 0.5–30 μm. It has been found that the center part of peaks is well approximated by the Voigt function with different Lorentz fractions, while the wing intensity drops faster and may be represented by a power function (with the index that varies from one structure to another). A well-marked dependence on the ordering of dislocations was observed. The drop in intensity in the majority of structures with a regular system and regular threading dislocations was close to the theoretically predicted law Δθ^–3; the intensity in films with a chaotic distribution decreased much faster. The dependence of the peak shape on the order of reflection, the diffraction geometry, and the epitaxial layer thickness was also examined.     

Long-term relaxation of parameters of surface layers of III–V compounds

We report the results of an experimental study of the long-term relaxation (LTR) of the electrophysical parameters of surface layers of InSb and InAs and the lattice constant after the action of a pulse of electric field. The results are explained on the basis of the assumption that the parameters of a surface layer undergo long-term relaxation as a result of its electrostimulated structural rearrangement.Translated from Izvestiya Vysshkikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 76–80, November, 1989.     

New approach to the X-ray diffraction analysis of test structures during flow calibration in epitaxial growth reactors

The high-resolution X-ray diffractometry (HRXRD) technique is known as a powerful tool for analyzing epitaxial heterostructures. However, standard analysis procedures do not allow the layer growth time to be used as a fixed parameter during HRXRD spectra analysis. The growth time in modern facilities is measured with a high degree of accuracy, which increases the reliability of HRXRD analysis particularly in the case of spectra with reduced quality or complex heterostructures consisting of a large number of individual homogeneous layers. A new algorithm is based on using flow rates of deposited components as variable parameters, while the layer growth times are taken as fixed parameters. A particular feature of this new approach is associated with the fact that the known growth time for each heterostructure layer is directly included into the algorithm for adjustment of the calculated spectrum to the experimental X-ray diffraction spectrum (HRXRD). The flows of deposited layers are variable parameters and, thus, the algorithm turned out to be very efficient for calibrating flow controllers in epitaxial growth reactors. The algorithm allows for reliable estimation of the flow even in the case of poorly informative HRXRD spectra.     

Nonlinear evolution of surface morphology in InAs/AlAs superlattices via surface diffusion

Continuum simulations of self-organized lateral compositional modulation growth in InAs/AlAs short-period superlattices on InP substrate are presented. The results of the simulations correspond quantitatively to the results of synchrotron x-ray diffraction experiments. The time evolution of the compositional modulation during epitaxial growth can be explained only including a nonlinear dependence of the elastic energy of the growing epitaxial layer on its thickness. From the fit of the experimental data to the growth simulations we have determined the parameters of this nonlinear dependence. It was found that the modulation amplitude does not depend on the values of the surface diffusion constants of particular elements.     

Investigation of the electrophysical and photoelectric properties of diffused layers of gallium arsenide obtained by compensation of copper

The distribution of the electrophysical and photoelectric properties of diffuse layers of p-GaAs obtained by doping copper using different diffusion modes is investigated. The properties of diffuse layers of p — n structures and volume specimens doped with copper over the whole depth are compared. The behavior of impurity centers is studied in these specimens and their effect on the electrophysical and photoelectric parameters of the material is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 95–100, October, 1977.In conclusion we thank I. V. Kamenskii for carrying out the experiments.     

Electrophysical properties of epitaxial layers of solid solutions of lead and tin tellurides doped with cadmium

Epitaxial layers of Pb_1−xSn_xTe (x≈0.2), undoped and doped with cadmium, are grown in a quasi-closed volume using the hot-wall method on BaF₂ fragments. The doping impurity is introduced directly into the material of the vapor source before synthesis in an equi-atom ratio with additional tellurium. The boundary of the limit of homogeneity from the side of the metallic components and in the region of the stoichiometric composition of the epitaxial layers doped with cadmium and the undoped epitaxial layers is established. The electrical conductivity and the Hall effect are investigated in the 77–450 K temperature range, and the temperature dependences of the intrinsic concentrations and of the ratio of the electron and hole mobilities are established. The temperature dependence of the Hall mobility is also investigated. The stability of the electrical parameters of the epitaxial layers are studied. It is shown that doping with cadmium enables highly stable n-type epitaxial layers to be obtained. Chernovits Branch, Institute of Problems of the Study of Materials, Academy of Sciences of Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 59–64, July, 1996.     

Evidence of very strong inter-epitaxial-layer diffusion in Zn-doped GaInPAs/InP structures

Zn-doped InP and GaInPAs layers were grown by OrganoMetallic Vapor-Phase Epitaxy (OMVPE). The epitaxial films consist of a primary GaInPAs/InP epitaxial layer and a secondary InP/GaInAs epitaxial layer. We present evidence that the redistribution of Zn acceptors in the primary epitaxial layer is strongly influenced by the Zn doping concentration in the secondary epitaxial layer. Rapid redistribution of Zn acceptors in the primary epitaxial layer occurs if the Zn doping concentration in the secondary epitaxial layer exceeds a critical concentration ofN _Zn3×10¹⁸cm^–3. The influence of the growth temperature on this effect is also presented.