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4H-silicon carbide ingots with high structural perfection have been grown by the modified Lely method (LETI method) on 100-mm-diameter seeds. Using our experimental data and theoretical analysis, we have systematized the key factors responsible for the degradation of the crystal structure of the ingots during the growth process. The formation of parasitic polytype inclusions in the early stages of growth has been shown to lead to the formation of antiphase boundaries and a mosaic substructure in the ingot.

The permittivity, conductivity, electric polarization, and features of high-resolution X-ray diffraction scattering of a relaxor ferroelectric PbCo1/3Nb2/3O3 have been investigated in the temperature range 5–350 K. Continuous correlated temperature changes in dielectric properties and electric polarization have been revealed, which were not typical of relaxor ferroelectrics. These changes can be attributed to local polar domains, which were induced in the original crystal matrix. In such domains, the charges (valences) of Co and Nb ions were continuously changed.

Epitaxial aluminum nitride (AlN) layers on Si(111) substrates have been grown by sequential application of several techniques including reactive magnetron sputter deposition to a thickness of 20 nm, metalorganic vapor-phase epitaxy (MOVPE) to a total thickness of 450 nm, and hydride vapor-phase epitaxy (HVPE) to a final thickness of 2 μm. Synthesis of AlN layers by this combined method provides a significant decrease in the residual strain and suppresses the formation of cracks in the epilayer.

Epitaxial layers of a new wide-band semiconductor (α-Ga2O3 doped with tin) have been grown by chloride epitaxy on smooth and patterned substrates, which are widely used to increase the emission yield in high-efficiency LED structures based on InGaN, and studied. The properties of the obtained gallium-oxide layers have been compared. Both types of samples had n-type conductivity, but the frequency and voltage dependences of their capacitance differed. Differences in the dislocation structure of epitaxial α-Ga2O3 layers on smooth and patterned substrates have been identified by X-ray diffractometry.

Semipolar GaN layers synthesized on a nanostructured Si(100) substrate are studied. It is shown that using a Si(100) nanoprofile combined with SixNy nanostrips on top of nanostructures can yield, via metal-organic chemical-vapor deposition, GaN(10 $$\bar {1}$$ 2) layers. An additional SiC buffer layer makes it possible to obtain GaN(10 $$\bar {1}$$ 1) layers with a full-width at half-maximum of the diffraction-curve of ωθ ≈ 35′ arcmin. It is found that the luminescence properties of the semipolar layers are mostly due to basal plane stacking faults BSFS-I1, in contrast to polar layers in which these properties are mostly due to the recombination of excitons.

Synthesis of AlN and GaN layers on a Si(100) substrate by chloride vapor-phase epitaxy has been considered. The process includes sulfidizing of the silicon surface, nucleation and growth of an AlN layer, and then formation of a GaN/AlN structure. It has been found that in the case of a (100)Si substrate, GaN nucleates on buffer AlN layers that may have two crystallographic orientations in contrast to a Si(111) substrate, on which a buffer layer may have only one orientation. It has been shown that the treatment of the Si(100) substrate in an aqueous solution of (NH4)2S decreases the FWHM of the rocking curve for GaN(0002) by a factor of 1.5.

Electric polarization in ErCrO3 single crystals has been investigated in the temperature range of 5_370 K. Ferroelectric ordering has not been found in any of the directions. However, electric polarization induced by restricted polar domains of structural origin has been observed. These domains are formed in the crystal matrix near impurity Bi^{3+} ions partially substituting Er^{3+} ions during the growth of single crystals by the method of spontaneous crystallization using solvent Bi_2O_3. The restricted polar domains form the superparaelectric state. Hysteresis loops with remanent polarization, both along the c axis and in the [110] directions, have been observed below some temperatures T_fr (in the frozen superparaelectric state). The polarization exists up to certain temperatures, which depend on the applied electric field orientation with respect to the crystal axes and exceed significantly temperature T_N of magnetic ordering., Comment: 15 pages, 6 figures

A comparative study of the dielectric properties and electric polarization of multiferroics GdMn2O5 and Gd0.8Ce0.2MnO5 has been carried out in the temperature range 5–330 K. The polarization properties in the ferroelectric state that forms due to a charge ordering and exchange striction have been studied at T ≤ TC = 30 K. The properties of the restricted polar phase separation domains formed in the crystals containing ions Mn3+ and Mn4+ have been studied, too. These domains exhibit the electric polarization in the temperature range from 5 K to some temperatures Tf ≫ TC. Such a high-temperature polarization is due to the frozen superparaelectric state of the restricted polar domains.

X-ray diffraction (XRD) in asymmetric Bragg geometry was measured and XRD intensity distribution maps in the reciprocal space were constructed for GaN epitaxial layers with various degrees of structural perfection grown on c-sapphire substrates. It is established that equal-intensity lines (isolines) related to a regular system of perpendicular rectilinear threading dislocations are extended in a direction parallel to the surface. For a more chaotic distribution of dislocations with a large fraction of horizontal fragments, these isolines are rotated toward a direction perpendicular to the reciprocal lattice vector, although they still not attain a limiting position characteristic of the ideal mosaic crystal.

We propose a new method for growing semipolar GaN films on a Si(100) substrate with an array of sub-100-nm-sized V-grooves formed on the surface. It is shown that, using such a nanostructured substrate for metalorganic hydride vapor-phase epitaxy, it is possible to obtain GaN (1011) epilayers deviating by an angle of about 62° from the polar direction and having an X-ray rocking curve with a minimum FWHM value of ωθ ~ 60 arcmin.

We have studied the influence of sulfide passivation on the initial stages of aluminum nitride (AlN)-layer nucleation and growth by hydride vapor-phase epitaxy (HVPE) on (100)-oriented single-crystalline silicon substrates. It is established that the substrate pretreatment in (NH4)2S aqueous solution leads to the columnar nucleation of hexagonal AlN crystals of two modifications rotated by 30° relative to each other. Based on the sulfide treatment, a simple method of oxide removal from and preparation of Si(100) substrate surface is developed that can be used for the epitaxial growth of group-III nitride layers.

The electric polarization induced by local polar domains of two types (phase separation domains of magnetic nature and structure-distorted domains) has been observed in YCrO3 single crystals. These domains form a superparaelectric state. Below some temperatures, in the frozen superparaelectric state, the pyrocurrent maxima and the hysteresis loops with remanent polarization are observed as along axis c so in directions [110]. The polarization exists to the temperatures depending on the orientation of electric field with respect to the crystal axes. The sources of formation of such local domains are analyzed and their properties are studied., Comment: 20 pages, 7 figures

The problem of prevention of AlN crystal layers from cracking under action of thermoelastic stresses during growth of these layers on SiC substrates has been studied. Calculation of residual thermoelastic stresses in AlN/SiC double-layer system has shown that cracking of the AlN layer during cooling is inevitable until this layer becomes at least 15 times thicker than a substrate. The required ratio of the thicknesses of the layer and the substrate can be reached by growing an AlN layer with simultaneous evaporation of the SiC substrate. Experimentally performed evaporation of SiC substrates in one process with growing AlN single layers on them using the sublimation sandwich method has made it possible to prevent these layers from cracking. Continuous (non-cracked) plates with 0.2–0.8 mm thickness without substrates have been obtained as a result of these experiments. According to X-ray images obtained in synchrotron radiation, they consist of single crystalline AlN of 2H polytype, contain dislocations, but do not contain cracks. The degree of crystallinity of these thin plates, which was estimated by the full widths at half-maximum of rocking curves of X-ray diffraction reflections, corresponds to the degree of crystallinity of thick (3–5 mm) AlN layers grown on nonevaporated SiC substrates.

The formation of the block structure and residual stresses in sapphire single-crystal tubes grown from the melt by the Stepanov method has been studied. The distribution of the difference in the residual stress tensor components (σφ–σr) in a thick-walled [0001] sapphire tube has been measured by the conoscopy method. It has been shown that circumferential tensile σφ and compressive stresses act on the outer and inner tube surfaces, respectively. The maximum stress is ∼20 MPa. It has been demonstrated that the development of the block structure begins from the outer tube surface; as the crystal length increases during growth, blocks propagate over the entire cross section.

The structure of short-period hexagonal GaN/AlN superlattices (SLs) has been investigated by X-ray diffraction. The samples have been grown by metalorganic vapor-phase epitaxy (MOVPE) in a horizontal reactor at a temperature of 1050°C on (0001)Al2O3 substrates using GaN and AlN buffer layers. The SL period changes from 2 to 6 nm, and the thickness of the structure varies in a range from 0.3 to 1 μm. The complex of X-ray diffraction techniques includes a measurement of θ-2θ rocking curves of symmetric Bragg reflection, the construction of intensity maps for asymmetric reflections, a measurement and analysis of peak broadenings in different diffraction geometries, a precise measurement of lattice parameters, and the determination of radii of curvature. The thickness and strain of separate SL layers are determined by measuring the θ-2θ rocking curves subsequent simulation. It is shown that most SL samples are completely relaxed as a whole. At the same time, relaxation is absent between sublayers, which is why strains in the AlN and GaN sublayers (on the order of 1.2 × 10−2) have different signs. An analysis of diffraction peak half-widths allows us to determine the densities of individual sets of dislocations and observe their change from buffer layers to SLs.

The electric and structural characteristics of silicon-doped GaN and Al0.3Ga0.7N layers grown by molecular beam epitaxy (MBE) using silane have been analyzed by the Hall effect, Raman spectroscopy, and high-resolution X-ray diffractometry. It is established that the electron concentration linearly increases up to n = 4 × 1020 cm−3 with an increase in the silane flow rate for GaN:Si, whereas the corresponding dependence for Al0.3Ga0.7N:Si is sublinear and the maximum electron concentration is found to be n = 4 × 1019 cm−3. X-ray measurements of sample macrobending indicate a decrease in biaxial compressive stress with an increase in the electron concentration in both GaN:Si and Al0.3Ga0.7N:Si layers. The parameters of the dislocation structure, estimated from the measured broadenings of X-ray reflections, are analyzed.

Using Si(As, P, B) and GaSb(Si) study, possibilities of X-ray diffraction methods for diagnostics of highly doped semiconductor crystals in characterization of dopant state - whether it is in the crystals in the form of solid solution or under various stages of its decomposition - are shown. The combination of techniques of X-ray diffraction topography and high resolution X-ray diffractometry, higher sensitive to the crystal lattice strain than that traditionally used is taken as the basis for investigating the crystals with slight and strong absorption of X-rays. These methods were supplemented with digital processing of the topographic images of growth striations and electrical measurements.

A new method of synthesis of semipolar gallium nitride on a silicon substrate using the technology of solid-phase epitaxy of 3C-SiC nanocrystals has been suggested. It has been demonstrated that application of buffer layers of 3C-SiC and AlN enables one to form epitaxial layers of semipolar gallium nitride with layer deviation from the polar position of the c axis of a wurtzite crystal by an angle of 48°–51° at the minimal half-width of the X-ray diffraction rocking curve (ωθ) ∼ 24′. The observed bend of a cylindrical character in the structure of GaN/AlN/3C-SiC(001) is explained by the anisotropic deformation of semipolar GaN on silicon.

A new approach to the deposition of aluminum nitride (AlN) layers with thicknesses ranging within ∼0.1–10 μm on silicon single crystal substrates by hydride-chloride vapor-phase epitaxy (HVPE) has been developed and implemented, which involves the formation of thin (∼100-nm-thick) intermediate silicon carbide (3C-SiC) interlayers. It is established that wavy convex bands with a height of about 40 nm are present on the surface of as-grown AlN layers, which are situated at the boundaries of blocks in the layer structure. It is suggested that the formation of these wavy structures is related to morphological instability that develops due to accelerated growth of AlN at the block boundaries. Experiments show that, at low deposition rates, AlN layers grow according to a layer (quasi-two-dimensional) mechanism, which allows AlN layers characterized by half-widths (FWHM) of the X-ray rocking curves of (0002) reflections about ωθ = 2100 arc sec to be obtained.

Si(As, P, B) and GaSb(Si) single crystals are used as examples to demonstrate the possibilities of methods of X-ray diffraction for the diagnostics (examination of a real structure) of highly doped semiconductor crystals. Prominence is given to characterizing the state of impurity: whether it is in a solid solution or at a certain stage of its decomposition. An optimum combination of X-ray diffraction methods is found to obtain the most complete information on the microsegregation and structural heterogeneity in crystals with low and high X-ray absorption. This combination is based on X-ray diffraction topography and X-ray diffractometry methods having an increased sensitivity to lattice strains.

Concentration and structural inhomogeneities in highly doped GaSb(Si) single crystals grown under various conditions of heat and mass transfer are studied by methods of X-ray topography, high-resolution X-ray diffractometry, and digital image processing. It is established that the inhomogeneity of crystals is determined by specific features of impurity microsegregation during growth under conditions of nonstationary convection in a melt and by peculiarities of the dislocation structure of crystals. The processes related to the initial stage of the decay of the Si supersaturated solid solution in GaSb contribute considerably to the inhomogeneity of crystals on the micro- and macrolevels.

The structural state of GaN epitaxial layers grown on r-plane sapphire through metal-organic vapor phase epitaxy has been investigated using X-ray diffraction. The interplanar spacings in two directions in the (11\( \bar 2 \)0) plane of the interface and in the direction perpendicular to it, as well as the diffraction peaks in the ϑ and ϑ-2ϑ scan modes in the Bragg and Laue geometries, are measured on double- and triple-crystal diffractometers. The intensity distribution maps for asymmetric Bragg reflections are constructed for two azimuthal positions of the sample. An analysis of the data obtained has demonstrated that the elastic strain is anisotropic and that the X-ray diffraction pattern parallel to the interface plane is broadened. The layers are contracted in the [1\( \bar 1 \)00] direction and unstrained in the [0001] direction. The broadening of the Bragg reflections in the [1\( \bar 1 \)00] direction is considerably larger than that in the [0001] direction. It is shown using the Williamson-Hall plots for the Bragg and Laue reflections that these broadenings are not related to different degrees of mosaicity but are determined by the local dilatations and misorientations around defects. The data obtained are analyzed, and the conclusions regarding the dislocation structure of the samples are drawn.

Structural state of nonpolar a-plane GaN layers grown by MOVPE on r-plane sapphire is investigated by X-ray diffraction method. Interplanar spacings were measured in three directions and corresponding strains were determined. A crystalline perfection was studied by measurement of diffraction peaks of θ- and θ-2θ-scanning in Bragg- and Laue-diffraction geometry. Their FWHM was analyzed by Williamson-Hall plots. Anisotropy of the elastic strains and the peak broadening was revealed. It is shown that a different broadening of diffraction pattern in two in-plane directions is not caused by mosaicity and can be explained by a specific distribution of dislocations.

A new approach is described, according to which the use of a thin silicon carbide (SiC) interlayer ensures the suppression of cracking and the simultaneous release of elastic strain in gallium nitride (GaN) epilayers grown by hydride-chloride vapor-phase epitaxy (HVPE) on 1.5-inch Si(111) substrates. Using this method, 20-μm-thick GaN epilayers have been grown by HVPE on Si substrates with AlN (300 nm) and SiC (100 nm) interlayers. A high quality of the obtained GaN epilayers is confirmed by the photoluminescence spectra, where an exciton band with hvmax = 3.45 eV and a half-width (FWHM) of 68 meV is observed at 77 K, as well as by the X-ray rocking curves exhibiting GaN(0002) reflections with a half-width of ωϑ = 600 arc sec.

X-ray diffraction, photoluminescence, micro-cathodoluminescence, and scanning and transmission electron spectroscopy were used to study the 710 MeV Bi ion irradiation effect in the fluence range of 1.4 × 109−5 × 1010 cm−2 on the structural and optical characteristics of pure high-resistivity n-type 4H-SiC epitaxial layers grown by chemical vapor deposition. It was established that the distribution of structural damage along the ion trajectory follows the computed profile of radiation defects formed in elastic collisions. The high-density ionization effect on the material characteristics has not been found under the irradiation conditions used. Optical methods revealed a wide spectrum of radiation-induced defects, with some of them contributing to the recombination process. The damaged 4H-SiC crystal lattice party recovers after annealing at 500°C.

The n{sup +}-6H/n-3C/p{sup +}-6H-SiC structure was fabricated for the first time by sublimation epitaxy, with mesa diodes formed on its base and their electrical characteristics were studied. It was found that a green band dominates in the spectrum of injection electroluminescence (EL) of these diodes. The band is close by its parameters to that associated with free-exciton recombination in bulk 3C-SiC, but is shifted by {approx}0.06 eV to shorter wavelengths. A similar effect was observed previously for triangular quantum wells in an n{sup +}-6H-SiC/p-3C-SiC heterojunction. An analysis of the experimental data obtained demonstrated that the structure can be regarded as two independent heterojunctions. The EL spectrum observed may be associated with radiative recombination at the n{sup +}-6H-SiC/n-3C-SiC heterointerface.

High-resolution x-ray diffractometry and electron microscopy are used to study the defect structure and relaxation mechanism of elastic stresses in AlGaN/GaN superlattices grown by the MOCVD method on sapphire covered with a preliminarily deposited GaN and AlGaN buffer layer. Based on an analysis of the half-widths of three-crystal scan modes of x-ray reflections measured in different diffraction geometries, the density of different dislocation families is determined. For all the dislocation families, the density is shown to increase with the Al concentration in the solid-solution layers and depend only weakly on the superlattice period. From the electron-microscopic patterns of planar and cross sections, the types of dislocations and their distribution in depth are determined. It is shown that, in addition to high-density vertical edge and screw dislocations, which nucleate in the buffer layer and propagate through the superlattice layers, there are sloped intergrowing dislocations with a large horizontal projection and bent mixed dislocations with a Burgers vector $$\left\langle {11\overline 2 3} \right\rangle $$ at the interface between individual superlattice layers. The former dislocations form at the interface between the buffer layer and the superlattice and remove misfit stresses between the buffer and the superlattice as a whole, and the latter dislocations favor partial relaxation of stresses between individual superlattice layers. In samples with a high Al concentration (greater than 0.4) in AlGaN layers, there are cracks surrounded by high-density chaotic horizontal dislocations.

Epitaxial silicon carbide layers of 3C-SiC polytype with an array of nanodimensional SiC quantum dots (QDs) have been obtained for the first time using an improved method of sublimation epitaxy in vacuum. The X-ray topography and X-ray diffraction data unambiguously confirm the formation of a 3C-SiC epilayer with twinned regions on the surface of a 6H-SiC substrate. The surface topography of epilayers was studied by atomic force microscopy (AFM), and the microstructure of a near-surface layer of the deposit was investigated by transmission electron microscopy (TEM). Using the AFM and TEM data, the presence of QDs (representing SiC nanoislands) is established, and their average dimensions and concentration are evaluated.

The dielectric response (100 Hz to 6 MHz), relaxation-time distribution, dielectric hysteresis loops and polarization obtained from pyroelectric current have been studied in the Cd 2 Nb 2 O 7 pyrochlore the ferroelectric (FE) state of which is frustrated due to embedded polar nanoregions of the nonergodic relaxor state (NERS). It is found that at frequencies below 1.5 MHz for dc bias electric fields of < 7 kV/cm the contribution of a relaxor state dominates over that of a normal FE state. A proper formation of glassy or FE properties of the NERS is prearranged during zero-field cooling and field cooling the system through the freezing temperature T f ≈ 182 K, respectively.

The idea of a new method for growing gallium nitride (GaN) epilayers in semi-polar direction by hydride-chloride vapor-phase epitaxy (HVPE) is disclosed. We propose to use Si(210) substrates with the first buffer layer of silicon carbide (3C-SiC) and the second buffer layer of aluminum nitride (AlN). It is experimentally demonstrated for the first time that, under conditions of anisotropic deformation in the GaN/AlN/3C-SiC/Si(210) structure, a GaN epilayer exhibits growth in semi-polar directions.

Three-crystal x-ray diffractometry is used for structural studies of nitride AlGaN/GaN superlattices (SLs) grown by metal-organic chemical vapor deposition on sapphire with GaN and AlGaN buffer layers with widely varied SL period (from 50 to 3500 A), Al content in Alx Ga1−x N layers (0.1≤x≤0.5), and buffer layer composition. Satellite peaks characteristic of SLs are well pronounced up to the third order in θ-2θ scans of symmetric Bragg reflections and θ scans of the symmetric Laue geometry. The corresponding curves are well modeled by kinematic formulas. The average SL parameters, as well as the thickness, composition, and strain of individual layers, are determined using a combination of symmetric Bragg and Laue reflections. It is shown that all the samples under study are partially relaxed structures in which the elastic stresses between the entire SL and the buffer layer, as well as between individual layers, are relaxed. The AlGaN layers are stretched and the GaN layers are compressed. The GaN layer compression is larger in magnitude than the AlGaN layer tension because of thermoelastic stresses.

Mirror-smooth, transparent bulk GaN layers with an area of 2×3 cm2 and a thickness of up to 1 mm were grown by hydrochloride vapor-phase epitaxy. Cracking of the material was eliminated by using a two-stage growth process; separation from a substrate was provided by a low-temperature buffer layer of preset thickness. For the best samples, FWHM of the X-ray rocking curve was ωθ=3.5′ and the dislocation density amounted to 107–108 cm−2.

The weak-field dielectric dispersion studies (100 Hz-13 MHz, 100K

Specularly smooth transparent layers of gallium nitride have been prepared of an area up to 2 x 3 cm 2 and thickness up to 1 mm. Growth of GaN wafers was implemented by HVPE, to eliminate cracking of the layers the process was carried out in two stages; separation of the GaN layer from the substrate was achieved by low-temperature deposition of a buffer layer of optimum thickness. FWHM of the X-ray rocking curve in the best samples is ω θ = 3.5' and the dislocation density is 10 7 -10 8 cm -2 .

Features of the creation of gallium arsenide (GaAs) p-i-n structures on germanium substrates are considered. Optimum regimes for growth of thick GaAs layers by hydride-chloride vapor phase epitaxy (HVPE) on Ge substrates are established, which allow high-quality p-i-n structures with characteristics close to those reached by homoepitaxy to be obtained. The spectra of exciton photoluminescence have been measured for ultrahigh-purity GaAs layers of various thicknesses grown under differing HVPE conditions.

The idea of a new method for growing gallium nitride (GaN) epilayers on (100)-oriented silicon substrates is disclosed. It has been experimentally established that the formation of a special oriented thin (600 nm) buffer layer of aluminum nitride (AlN) by hydride-chloride vapor-phase epitaxy (HVPE) makes possible the growth of GaN in semi-polar direction. For the best epilayers obtained by this method, the X-ray rocking curve half-width is ωθ(0004) = 30 arcmin. The photoluminescence spectra of GaN films measured at 77 K exhibit both exciton and donor-acceptor recombination bands.

The parameters of deep-level centers in lightly doped 4H-SiC epilayers grown by sublimational epitaxy and CVD were investigated. Two deep-level centers with activation energies E-c - 0.18 eV and E- ...

The structural perfection of silicon carbide substrates and homoepitaxial layers grown on the substrates by sublimation has been studied by x-ray diffraction (topography and diffractometry) and optical microscopy. The optimum diffraction conditions (hkil reflections, radiation wavelength λ, and recording geometry) for revealing “micropipes” of the dislocation nature are determined. It is shown that the growth conditions used make it possible to obtain highly perfect epitaxial layers.

The Gd3+ EPR spectroscopy, radio-frequency (100 Hz — 1 MHz) diaelectric dispersion and X-ray diffraction studies of Cd2Nb2O pyrochlore over the temperature range of 80 K-300 K are presented and discussed from the viewpoint of structure instability and structure imperfection of the system.

Two-and three-crystal diffractometric study of the structural perfection of GaN epitaxial films grown on sapphire, GaAs, and SiC substrates is reported. The diffraction intensity distributions around the reciprocal-lattice points are shown to be extended in the direction parallel to the surface, which is connected with the anisotropy of the local strain fields in the layers. A comprehensive analysis is made of the broadening for several reflection orders measured in three geometries, namely, Bragg, symmetric Laue, and grazing-angle diffraction. The five independent components of the microdistorsion tensor δe ij , as well as the average coherent-scattering lengths in two directions, τ z and τ x , have been obtained. It is shown that for most samples the components responsible for reflection broadening along the surface are noticeably larger, i.e. δe xx >δe zz , and δe zx >δe xz , as well as τ z >τ x . All tensor components are related to a specific dislocation type. Electron microscopy of the samples revealed a high density of pure edge and pure screw dislocations extending normal to the interface, and which provide a dominant contribution to e xx and e zx , respectively.

First results of the electron-microscopic investigation of thin silicon carbide (SiC) layers grown on silicon using a new method of solid phase epitaxy are presented. It is shown that, at the initial stage of epitaxial growth, a transition layer is formed which consists of various SiC polytypes. This layer occurs at the interface between the substrate and a single-crystalline SiC layer possessing predominantly a 3C polytype structure. It is established that pores with dimensions ranging from a fraction of micron to several dozen nanometers are formed in a near-surface layer of the silicon substrate, which favor the growth of epitaxial, weakly strained single-crystalline SiC layers.

Epitaxial 3C-SiC films grown on the (0001)C face of 6H-SiC substrates by sublimation epitaxy in vacuum have been studied. The results of x-ray diffraction measurements show evidence of a rather high structural perfection of silicon carbide epilayers. The Raman spectroscopy data confirm that the 3C-SiC layer grows immediately on the 6H-SiC substrate without any transition layers. It is concluded that the structures under consideration are well suited for the investigation of a two-dimensional electron gas at the 3C-SiC/6C-SiC heterojunction

3C-SiC epitaxial layers with a thickness of up to 100 µm were grown on 6H-SiC hexagonal substrates by sublimation epitaxy in vacuum. The n-type epitaxial layers with the area in the range 0.3–0.5 cm2 and uncompensated donor concentration N d − N a ∼ (1017–1018) cm−3 were produced at maximum growth rates of up to 200 µm/h. An X-ray analysis demonstrated that the epitaxial layers are composed of the 3C-SiC polytype, without inclusions of other polytypes. The photoluminescence (PL) spectrum of the layers was found to be dominated by the donor-acceptor (Al-N) recombination band peaked at hv ≈ 2.12 eV. The PL spectrum measured at 6 K was analyzed in detail. It is concluded that the epitaxial layers obtained can serve as substrates for 3C-SiC-based electronic devices.

The structure and luminescent properties of gallium nitride (GaN) epilayers grown by hydride-chloride vapor-phase epitaxy (HVPE) in a hydrogen or argon atmosphere on 2-inch Si(111) substrates with AlN buffer layers have been studied. The replacement of hydrogen atmosphere by argon for the HVPE growth of GaN leads to a decrease in the epilayer surface roughness. The ratio of intensities of the donor-acceptor and exciton bands in the luminescence spectrum decreases with decreasing growth temperature. For the best samples of GaN epilayers, the halfwidth (FWHM) of the X-ray rocking curve for the (0002) reflection was 420 sec of arc, and the FWHM of the band of exciton emission at 77 K was 48 meV.

This paper discusses how the processing parameters affect the structural perfection of epitaxial layers of 3C-SiC grown on 6H-SiC substrates by vacuum sublimation. It shows that, at constant temperature and using virtually undisoriented substrates, decreasing the growth rate increases the size of the twinning regions in the films and reduces the total defect concentration of the 3C/6H structures. Epitaxial layers of 3C-SiC with a defect density of 101–102 cm−2 and a twinning area of up to 6 mm2 have been obtained.

Bulk GaN layers with a thickness of up to 1.5 mm and a lateral size of 50 mm were grown by hydride-chloride vapor-phase epitaxy (HVPE). The best samples show a half-width (FWHM) of the X-ray rocking curve of ωθ=27′, a charge carrier density of ∼8 × 1019 cm−3, and a mobility of ∼50 cm2/(V s). The photoluminescence spectra of the obtained epitaxial GaN layers exhibit an edge emission band at 348 eV. The HVPE layers are characterized by a high mechanical strength: HV = 14 GPa.

Spectra of deep centers in a lightly doped 6H-SiC substrate having regions with different degrees of structural perfection were investigated. It is found that the concentrations of the majority of deep centers are independent of the dislocation density in a given region of the sample. The obtained results and published data lead to the conclusion that the concentration of silicon vacancies is independent of the degree of the structural perfection of 6H-SiC.

X-ray topography and diffractometry are used to study the crystal structure of cadmium pyroniobate Cd2Nb2O7 at room temperature. Structural quality parameters were determined for crystals grown with different degrees of impurity doping. The nature of the crystal lattice damage is analyzed as a function of the type and concentration of impurities.