共查询到20条相似文献,搜索用时 15 毫秒
1.
I. A. Subbotin M. A. Chuev E. M. Pashaev R. M. Imamov G. B. Galiev S. A. Tikhomirov P. Kacerovsky 《Crystallography Reports》2007,52(4):611-617
The structural characteristics of the P-HEMT AlGaAs/InGaAs/GaAs heterostructure have been studied by high-resolution X-ray diffractometry. The parameters of the heterostructure layers were determined by simultaneous analysis of the X-ray reflection curves for the (004) and (113) crystallographic planes. Interface diffusion has been established for the InyGa1?yAs quantum well and the AlxGa1?x As spacer layer, which are characterized by reconstructed profiles of the lattice parameter distribution and anisotropic distribution of random displacements in the layer plane and in the perpendicular direction. 相似文献
2.
A. M. Afanas’ev M. A. Chuev R. M. Imamov É. Kh. Mukhamedzhanov M. M. Rzaev F. Schäffler M. Müehlberger 《Crystallography Reports》2002,47(6):1058-1062
The structural characteristics of silicon samples containing one and two Si1 ? x Gex/Si quantum wells 1.8 to 15 nm thick were determined by high-resolution X-ray diffraction. A detailed analysis of X-ray rocking curves made it possible to reproduce the Ge-concentration profiles in the quantum wells. The diffusion of germanium (up to 20%) into interface layers was observed, with a consequent broadening of the quantum well interfaces. 相似文献
3.
The structure of the interfaces of a 10-nm-thick InxGa1 ? x As quantum well buried in the semiconductor GaAs matrix has been studied by the method of double-crystal X-ray diffractometry. It has been shown that, in comparison with the well-known photoluminescence method, the X-ray diffraction method has considerable advantages in characterization of multilayer systems. The detailed analysis of the rocking curves provided the reconstruction of the profiles of indium distributions in quantum wells for specimens with different indium concentrations. 相似文献
4.
In this paper we present the performance of GaP AlxGa1−xP heterostructure waveguides for integrated optic hybrid devices. The waveguide layer is graded with a parabolic refractive index profile for the light emission of a DH GaAs semiconductor laser. The waveguide heterostructure performed allows to couple at it edge crossection semiconductor laser or photodetector as well as fix or solder them on the same substrate on which the heterostructure layers were deposited. The heterostructure layers were grown by liquid phase epitaxy and the heterostructure waveguide was performed by means of etching technics specially developed for this purpose. Both, the growth procedure, as well as the etching technics are described. The results achieved are shown in curves and photographs, taken on a scanning microscope. 相似文献
5.
G. B. Galiev I. S. Vasil’evskii R. M. Imamov E. A. Klimov S. S. Pushkarev I. A. Subbotin 《Crystallography Reports》2011,56(5):875-879
A complex study of the structural and electrical properties of nanoheterostructures containing a metamorphic barrier with
a high InAs content (37–100%) in the active region have been performed by the Van der Pauw and X-ray diffraction methods.
All peaks observed in the rocking curves for the samples studied (throughout the entire structure) have been revealed and
identified. It is shown that, having properly chosen the design of the metamorphic buffer and the compositional gradient in
it, one can obtain mobilities and concentrations of the 2D electron gas in the In
x
Ga1−x
As quantum well in the heterostructures formed on GaAs substrates that are comparable with the corresponding values for the
nanoheterostructures grown on InP substrates. It is established that the mobility and concentration of 2D electron gas depend
both on the metamorphic barrier design and on the structural quality of heterostructure as a whole. 相似文献
6.
The crystallographic parameters of elements of a metamorphic high-electron-mobility transistor (MHEMT) heterostructure with In0.4Ga0.6As quantum well are determined using reciprocal space mapping. The heterostructure has been grown by molecular-beam epitaxy (MBE) on the vicinal surface of a GaAs substrate with a deviation angle of 2° from the (001) plane. The structure consists of a metamorphic step-graded buffer (composed of six layers, including an inverse step), a high-temperature buffer of constant composition, and active high-electron-mobility transistor (HEMT) layers. The InAs content in the metamorphic buffer layers varies from 0.1 to 0.48. Reciprocal space mapping has been performed for the 004 and 224 reflections (the latter in glancing exit geometry). Based on map processing, the lateral and vertical lattice parameters of InxGa1–xAs ternary solid solutions of variable composition have been determined. The degree of layer lattice relaxation and the compressive stress are found within the linear elasticity theory. The high-temperature buffer layer of constant composition (on which active MHEMT layers are directly formed) is shown to have the highest (close to 100%) degree of relaxation in comparison with all other heterostructure layers and a minimum compressive stress. 相似文献
7.
R. Beanland 《Journal of Crystal Growth》1993,130(3-4):394-404
Double-crystal X-ray diffraction is commonly used to measure the misfit strain and relaxation of epitaxial semiconductor layers. In this paper, a framework is developed which links the measured parameters Δd / d and Δø to the deformation tensor of a semicoherent layer. Isotropic elasticity theory and the Frank-Bilby equation are used to derive an analytical expression for this deformation. By combining X-ray measurements of different planes, it is possible to obtain the misfit strain and details of the misfit dislocation array in a strained layer grown on a substrate of arbitrary orientation. In (001) layers, it is shown that the misfit strain and relaxation can be found from just six rocking curves, although the most accurate measurements require twelve rocking curves. 相似文献
8.
The growth and structure of (1-1.5)-μm-thick Pb1?x Mn x Te(Ga)(x = 0.06) films with 0.4?0.9 at % of gallium, grown on BaF2(111) and Pb1?x Sn x Te (x = 0.2) (100) substrates by molecular beam epitaxy, have been investigated. It is established that the films are crystallized into an fcc structure, and their growth planes are (111) and (100), according to the substrate orientation. The optimal conditions for obtaining high-resistivity photosensitive p-and n-type films with a perfect crystal structure (W 1/2 = 80″?100″) have been determined. 相似文献
9.
a-Si1?xCx:H films are deposited by RF plasma enhanced chemical vapor deposition (PECVD) at different RF powers with hydrogen-diluted silane and methane mixture as reactive gases. The structure and properties of the thin films are measured by infrared spectroscope (IR), Raman scattering spectroscope and ultra violet–visible transmission spectroscope (UV–vis), respectively. Results show that the optical band gap of the a-Si1?xCx:H thin films increases with increasing Si–C bond fraction. It can be easily controlled through controlling Si–C bond formed by modulating deposition power. At low deposition power, the bond configuration of the a-Si1?xCx:H thin film is more disordered owing to the distinct different bond lengths and bond strengths between Si and C atoms. At a too high deposition power, it becomes still high disordered due to dangling bonds appearing in the a-Si1?xCx:H thin film. The low disordered bond configuration appears in the thin film deposited with moderate deposition power density of about 2.5 W/cm2. 相似文献
10.
La1−xSrxMnO3−σ (LSMO) thin films have been grown on SrTiO3 (0 0 1) single-crystal substrates using the laser molecular beam epitaxy (MBE) technique. The two-dimensional layer-by-layer growth was in-situ monitored by reflection high-energy electron diffraction (RHEED). Kinetic growth with surface relaxation was also observed, and crystallinity of the thin films was investigated by high-resolution X-ray diffraction. Results of 2θ−ω scans revealed a strong correlation between out-of-plane lattice constant and oxygen content as well as strontium doping concentration. However, further analysis of rocking curve measurements around (0 0 2) plane of thin films grown under different oxygen pressure (PO2) shown the effects of oxygen content on the crystal structure. An exceptionally low full-width at half-maximum (FWHM) of 0.02° was measured from the sample grown at PO2 of 5.0 Pa, indicating the almost perfect epitaxial growth of LSMO thin films. 相似文献
11.
Single- and double-heterojunction structures of AlxGa1?xP/GaP were grown by liquid phase epitaxy and their opto-electronic properties were characterized. Using a starting growth temperature of 900°C, a background impurity level in undoped Al0.5Ga0.5P of 1 × 1016 cm-3 (p-type) is obtained. The growth rate of AlxGa1?xP was very low. An almost intrinsic layer exists at the p-n AlxGa1?xP/GaP heterojunction interface due to the interdiffusion of the dopants. By using a rotating slide liquid phase epitaxial growth technique, we have made a high efficiency light modulator from a AlxGa1?xP/GaP double heterostructure. The employment of a dummy crystal resulted in very good reproducibility of the GaP waveguide layer thickness. Light is well confined in the GaP layer and a voltage difference, Vπ, of 6 V is enough to obtain the phase difference, π, between TE and TM modes. 相似文献
12.
A technique for the computer modeling of disordered binary oxide solid solutions MO-M′O in a wide composition range has been developed. The method of atomistic pair potentials was used for 4 × 4 × 4 supercells. The parameters of the potentials are optimized using the structural and elastic properties of pure components MgO, CaO, SrO, and BaO. The temperature dependences of the heat capacity and entropy are calculated for pure components. The excess mixing properties (enthalpy, volume, bulk modulus, vibrational entropy) are found for different compositions of Mg x Ca(1 ? x)O, Ca x Sr(1 ? x)O, and Sr x Ba(1 ? x)O solid solutions. Temperature and composition dependences of the excess Gibbs energy were constructed, which made it possible to approximately estimate the critical decomposition temperatures and limits of component miscibility. Statistical analysis of lattice distortions in the first and second coordination spheres reveals a detailed picture of the solid-solution local structure. 相似文献
13.
The article continues a series of publications on the technologically important multilayer InxGa1-x As-GaAs/GaAs system with the 3-, 6-, and 9 nm-thick layers (quantum wells). The collimation system of the incident beam is improved. The dimensions of quantum wells and the interfaces between these wells are determined. The qualitative picture of quantum well “spreading” is described. The experimental diffraction reflection curves are measured from three different parts of the specimen. Their analysis shows how homogeneous the structure grown is. 相似文献
14.
A software program has been developed for joint solution of the inverse problem on the basis of the X-ray diffractometry and reflectometry data. A system of basic objects supporting some functions of automatic data flow processing in the program and oriented to mathematical calculations has been created. It is shown by the example of experimental data for an In x Ga1 ? x As-In y Al1 ? y As/InP(001) sample that joint fitting of X-ray diffractometry and reflectometry curves makes it possible to reconstruct the model parameters of a multilayer with smaller rms errors. The data were processed taking into account the angular dependences of the background intensity and the aperture factors stemming from the geometry of the experiment. 相似文献
15.
G. B. Galiev S. S. Pushkarev I. S. Vasil’evskii E. A. Klimov R. M. Imamov I. A. Subbotin E. S. Pavlenko A. L. Kvanin 《Crystallography Reports》2012,57(6):841-847
A complex structural and electrophysical analysis of MHEMT In0.70Al0.30As/In0.75Ga0.25As nanoheterostructures grown on (100)GaAs substrates using two radically new designs of metamorphic buffer (providing different internal-strain distributions) has been performed. The lattice parameters of the constant-composition layers entering the metamorphic buffer have been determined by X-ray diffraction using symmetric and asymmetric (400) and (422) reflections. It is shown that, having chosen a proper design of metamorphic buffer in nanoheterostructures on GaAs substrates, it is possible to obtain electron mobility and concentration comparable with those for nanoheterostructures on InP substrates. The compositions of smoothing layers, determined from the peaks on rocking curves, are found agree well with the process values. 相似文献
16.
Single crystals of the α?-phase of (Zn1 ? x Cd x )3As2 solid solution (x = 0.26) have been prepared and investigated by X-ray diffraction analysis. The tetragonal unit-cell parameters are found to be a = b = 8.5377(2) Å, c = 24.0666(9) Å, sp. gr. I41/amd, Z = 16. Zn and Cd atoms in the crystal statistically occupy three symmetrically independent positions in the mirror planes and are tetrahedrally coordinated by arsenic atoms. (Zn,Cd) tetrahedra share edges to form a three-dimensional structure framework. The α?-phase is geometrically related to the fluorite structure. The character of arrangement of tetrahedral vacancies in fluorite-like unit cells is revealed. Chains of tetrahedral vacancies form microchannels oriented parallel the a and b axes, which pierce the three-dimensional structure framework at different levels along the c axis. The structure of α″-Cd3As2 crystals is found to be similar to that of α?-(Zn0.74Cd0.26)3As2. 相似文献
17.
The vapour growth of InAs1-xPx layers has been carried out by the hydride process. The phosphorus rich part of the system (0.7 ? x ? 1) was especially investigated. Heteroepitaxial deposits of InAs1-xPx and InP have been performed on substrates such as InAs, GaAs and GaP. A systematic study of the influence of the substrate orientation on the quality of the layer has been carried out by growth on hemispherical substrates. Preferential planes have been pointed out: (100) and (111) A for InAs, (111) for GaAs and GaP. The band gap variation as a function of the composition has been determined by photoluminescence at 4.2 °K and X-ray diffraction measurements. It fits the equation: EG(x) eV = 0.425 + 0.722 x + 0.273 x2 at 4.2 °K. 相似文献
18.
《Journal of Crystal Growth》1999,196(1):53-61
We have grown a multilayer structure of GaAs and AlxGa1−xAs (x=0.25) by molecular beam epitaxy at low substrate temperature (250°C) in order to investigate the effects of annealing on arsenic precipitation and vacancy-defect formation. The as-grown heterostructure contained ∼5×1017 cm−3 gallium vacancies, but information about the individual layers was lost because the layer width (∼45 nm) was smaller than the average positron diffusion length (∼70 nm). Annealing at 500 and 600°C showed increases in the S-parameter (above the bulk value) of ∼2.5% and ∼1.5%, respectively, smaller than for a single LT-GaAs layer (∼3–4%). We explain this phenomenon by suggesting that the excess arsenic which migrates from the material with the higher precipitate/matrix energy (LT-AlxGa1−xAs) reduces the gallium vacancy concentration in the LT-GaAs and hence the S-parameter. This hypothesis is supported by SIMS data which shows a build-up of As in the LT-GaAs layers, and TEM images which indicate that arsenic precipitation occurs to a greater extent in the LT-GaAs than in the LT-AlxGa1−xAs. 相似文献
19.
A new approach to application of diffuse scattering (DS) for studying the defect structure of crystals on laboratory radiation sources is implemented. The basic principles of this approach are as follows: (i) choice of crystals with a high concentration of structural defects (highly nonstoichiometric Ca1 ? x R x F2 + x phases), (ii) application of intermeasurement minimization method (experimental comparison) to select a weak desired DS signal from a superposition of signals of different nature, and (iii) choice of the basic model proceeding from the reliable information provided by accurate analysis of the contribution of structural defects to Bragg reflections. Significantly different DS diffraction patterns have been recorded for Ca0.87La0.13F2.13 and Ca0.92Er0.08F2.08 crystals, characterized by different types of structural-defect clusters, determined from the Bragg diffraction data. Experiments performed at 90–100 K proved that DS is caused by clusters with stable atomic configurations rather than cooperative thermal atomic vibrations. A set of methods is proposed which can efficiently be used in diagnostics of nanomaterials. 相似文献
20.
E. A. Sulyanova D. N. Karimov S. N. Sulyanov B. P. Sobolev 《Crystallography Reports》2014,59(1):14-21
A Sr0.7Ce0.3F2.3 crystal (CaF2 type, sp. gr. $Fm\bar 3m$ ), obtained by quenching from melt, has been studied for the first time by X-ray diffraction. Fluorine vacancies and interstitial anions are found in the 8c and 32f sites, respectively. The defect ratio in the Sr0.7Ce0.3F2.3 structure corresponds to the tetrahedral cluster configuration of defects {Sr4 ? n Ce n F26}. The defect structure of quenched (at a rate of ~25 K/min) crystal differs from that of a crystal grown from melt (cooling at a rate of ~3 K/min) by the displacement of some cations (presumably Ce3+) along the threefold axis to the 32f site and the anisotropy of thermal vibrations of ions in the cluster core (F int(32f)3). The concentration dependence of the lattice parameters of quenched Sr1 ? x Ce x F2 + x phases (x = 0–0.5) is described by a third-order polynomial: a = 5.80009 + 1.166518 × 10?3 x ? 1.124969 × 10?5 x 2 + 8.258155 × 10?8 x 3. The compositional dependence of microdistortions is also nonlinear; maximum microdistortions are observed in the SrF2 crystal. They decrease with an increase in the cerium concentration x to ~ 0.35. The minimum in the range x = 0.30–0.35 correlates with a composition corresponding to the peak (at x ~ 0.29) in the melting curves of the fluorite phase estimated from the phase diagram of the SrF2-CeF3 system (the method of thermal analysis). 相似文献