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We have analyzed phase equilibria in the Si–C–H–Ar system during silicon carbide ingot growth by the modified Lely method. The results indicate that the addition of even small amounts of hydrogen to an inert carrier gas leads to a sharp increase in the rate of carbon transport through the gas phase, mediated by volatile hydrocarbons, primarily acetylene, and prevents carbon enrichment in the solid source and corrosion of the graphite equipment in the single-crystal seed region.

The optical and photovoltaic properties of two-component TPP–Yt0.95Er0.05VO4 films prepared by the spincoating method are for the first time studied. A 30% increase in the photovoltage (PV) of TPP: Yt0.95Er0.05VO4 = 3: 2 films on silicon carbide (SiC) supports as compared to TPP one-component films is observed. In contrast, for films on tin dioxide (SnO2) supports, the PV drops by 35–96% as the TPP content in the film decreases from 80 to 20%. The properties of the films are monitored by atomic force microscopy. The highest roughness of the films corresponds to a 40–60% TPP content.

On the basis of both published data and our own experimental data we consider the main aspects of the problem related to ensuring polytype stability for ingots of grown 4H and 6H silicon-carbide compounds.

Model concepts of control over the formation of oxide shells in the course of oxidation are confirmed on the basis of experimental results obtained in a study of the fundamental aspects of how nanostructured layers are formed upon diffusion annealing on faceted single crystals of lead chalcogenides. Auger-spectroscopic data on the distribution of the elemental composition over the thickness of layers based on lead selenide–cadmium selenide solid solutions are presented.

Theoretical and experimental studies of the phenomenon of polytypism in silicon carbide obtained by the Lely method have been presented. It is shown that the elementary theory of polytypism can be built on the basis of very general considerations, taking into account the physical and chemical parameters of the growth process, as well as the steric factor and the possible symmetry of elementary clusters involved in the growth process.

Model concepts concerning control over the formation of oxide layers during the course of oxidation are developed on the basis of experimental results of studies of systematic features of the formation of nanostructured layers after diffusion annealing. Data on a variation in the composition of oxide phases as the extent of deviation from stoichiometry is changed in the initial lead chalcogenide are presented. Model concepts related to the possibility of varying the thickness of the coating oxide phases using annealing in an oxygen-containing medium are developed. It is shown that annealing in an iodine atmosphere ensures the effective penetration of oxygen into the grains, which is necessary for an increase in the photoluminescence efficiency.

The features of the defect structure of 4H silicon carbide ingots grown by the modified Lely method on (11\( \bar 2 \)2)-oriented seeds are studied. It is shown that this seed plane can be used to improve the structural quality of silicon carbide ingots. The defect structure of grown ingots features a complete lack of micropores and a decreased (by an order of magnitude) dislocation density in comparison with the seed. At the same time, growth on the (11\( \bar 2 \)2) seed results in stacking fault accumulation. The type of stacking faults corresponds to formula (5, 2) in the Zhdanov notation (internal Frank stacking fault).

The methods of optical microscopy and X-ray diffractometry have been used to study the features of defect structure in ingots of the SiC-4H polytype; the ingots have featured different diameters and have been grown by the modified Lely method on seeds with deviations of several degrees from the exact orientation (0001)C in the direction 〈11 $$ \bar 2 $$ 0〉 (off-cut (0001) seeds). The slip bands observed in the crystals are extended along the [11 $$ \bar 2 $$ 0] direction and correspond to the secondary slip system of threading dislocations a/3〈11 $$ \bar 2 $$ 0〉{ $$ \bar 1 $$ 100} for hexagonal close packing (HCP) crystals. Low-angle dislocation boundaries directed along [1 $$ \bar 1 $$ 00] accommodate the disorientation of neighboring domains, which results from their mutual rotation around the [0001] axis. Enlargement of ingots leads to some increase in the dislocation density, mainly due to threading edge dislocations. The average density of micropipes is in the range of 5–20 cm−2 and practically remains unchanged as the ingot size is increased.

The degree of structural perfection of 4H-polytype silicon carbide ingots grown by the modified Lely method was improved using a multistage process with sequential change in the seed orientation (similar to the previously suggested RAF process). The grown ingots 20–40 mm in diameter are characterized by an almost total absence of peripheral low-angle boundaries and a significant decrease in the micropore density (two-three orders of magnitude in comparison with the starting material). Repeated shouldering of obtained seeds with (000 $$ \bar 1 $$ )C orientation up to 50–55 mm in diameter results in insignificant deterioration of the structural quality in newly formed peripheral regions of the ingot. High-quality perfect silicon carbide wafers were obtained, characterized by a micropore and basal dislocation densities of 5–40 and 103–104 cm−2, respectively.

The growth of 4 H-polytype silicon carbide ingots by the modified Lely method on (10 $$ \bar 1 $$ 0) seeds has been investigated. It is shown that this seed plane allows intense ingot outgrowth. Single-crystal ingots up to 60 mm in diameter can be obtained at growth rates below 0.6 mm/h. Investigation of the defect structure showed that the grown ingots are practically micropipe-free but contain stacking faults and carbon inclusions.

The problem of the appearance of carbon inclusions in single-crystal silicon carbide ingots grown by the modified Lely method (the so-called graphitization of the ingot) is analyzed. It is shown that the process of graphitization of the ingot is not related to a deficit of silicon in the growth cell; in contrast, it is excess of silicon at the growth surface that inhibits the ingot growth rate and gives rise to intense corrosion of the graphite fittings.

An algorithm for the search of a domain structure appearing in a growing single crystal of silicon carbide on the emergence of syntaxic inclusions is presented. Experimentally observed crystal joints are analyzed.

A model that includes both thermophoretic force and advective flow is developed to describe the mechanism of appearance of carbon macroinclusions in silicon carbide ingots grown by modified-Lely technique. The main moving force acting on the carbon particle suspended in a gas ambient appears to be a drag force, thermophoretic force being essential only for the relatively low temperatures (T 20 K/cm). It is shown that the radius of suspended particles may achieve hundreds of micrometers, and the data of calculations are in agreement with the experiment.

Defects caused by 15R polytype inclusions in 4H silicon carbide ingots have been considered. Growth rate along with curvature of the interface determines the stability of the 4H-polytype reproduction. The domain structure arising in the 4H polytype as a result of foreign polytype inclusion has been analyzed. Antiphase domains of the 4H polytype emerging at the top and lateral sides of 15R inclusion form a strictly determined set of binary and ternary joints (extended threading defects). Junctions of a higher order could generate open-core threading superdefects.

The aim of the present paper is to discuss our results of the investigation (both theoretical and experimental) of mass transfer in the β-SiC–α-SiC system in conditions of about zero temperature gradient. Growth temperature was in the range 1800–2300°C. Modeling of growth of silicon carbide crystals have been carried out both for vacuum (10−3 Pa) and for a gas (nitrogen, argon or their mixture) atmosphere. The gas pressure was in the range 102–105 Pa. Growth rate in the range from 0.01 to 1.5 mm/h for growth in vacuum and 0.001–0.15 mm/h for growth in gas have been calculated. Experimental results obtained are in a good agreement with theoretically predicted ones.

The presence of slightly misoriented (less than 1°) comparatively large areas in silicon carbide boules grown by the sublimation method is one of the types of defects which can limit the operation of devices based upon such material. 6H- and 4H-SiC boules were grown by the modified Lely method elaborated at the St.-Petersburg Electrotechnical University. Formation of stress and misoriented areas in SiC crystals has been investigated. Nondestructive techniques for such material characterization have been developed.

The method of hot-wall epitaxy is used to grow epitaxial heterostructures of p-PbTe/n-PbS on BaF2 substrates. Hall-effect measurements are analyzed in order to obtain the dependence of the effective carrier mobility on thickness and temperature in the ranges 0.1–2 µm and 100–300 K, respectively. It is found that this mobility depends on the thickness of the sample and on the individual thicknesses of its constituent layers. The effective mobility is calculated under the assumption that charge carriers are scattered by the surface of the structure and by dislocations that form at the heterojunction boundary.

Interest in silicon carbide as a semiconductor suitable for fabricating devices operating under extreme conditions has increased sharply in recent years. The main problem now lies in the mass production of silicon carbide single crystals with a low defect density and high crosssectional uniformity of the properties. This study involves a numerical simulation of heat and mass transfer processes during growth of SiC single crystals by the sublimation method. The results obtained make it possible to trace the effect of the growth conditions on the temperature distribution and the distribution of the main components in the vapor phase, as well as the radial profile of the rate of growth of a single crystal for different stages of growth process.

A modified Ludeke model assuming that interfacial defect states are responsible for the formation of the Schottky barrier is applied to calculate the barrier heights Φbn in the systems 〈Ag, Au〉-〈3C-, 6H-SiC〉. Excellent agreement with experimental data is obtained. The calculation also shows that the concentration of silicon vacancies determining the Φbn value depends only slightly on the nature of the metal constituent of the contact.

The results obtained in measuring the Schottky barrier height Φ b n for a chromium contact with 8H-, 6H-, 15R-, 27R-and 4H-SiC silicon carbide polytypes with n-type conduction are analyzed in terms of a simple model. It is shown that the Φ b n value is proportional to the concentration of silicon vacancies in the polytypes. The results of Φ b n measurements for palladium and platinum contacts to silicon carbide polytypes are discussed.

A model of electrically active and neutral native point defects in SnO2 is developed. Thermodynamic analysis of the equilibrium of the native point defects makes it possible to construct the phase diagram \(P_{O_2 } - T - x\) of lead dioxide. The contradiction between n-type monopolar conductivity and the two-sided homogeneity region of the SnO2 phase is resolved.

The distribution of the elements in naturally faceted PbTe and Pb0.8Sn0.2Te single crystals doped with zinc and cadmium is analyzed. The results show the formation of a multilayer structure with an outer layer of ZnTe (CdTe) on top of a metallic sublayer.

The defect structure of 4H silicon carbide single crystals grown by PVT method on three prismatic seeds (10-10), (11-20) and (8.3.-11.0) is considered. The only defects existing in the grown ingots are stacking faults and basal plane dislocations. The type of stacking fault is studied. The dependence of stacking fault morphology on the seed orientation is analyzed.

The year 1990 marked the 35th anniversary of the publishing of the work of Lely [1] in which the growth of semiconducting silicon carbide single crystals by spontaneous crystallization from the vapor at 2550–2600 ¼ was reported. During these years, numerous attempts have been made to perfect the method by optimizing the thermal fields in the growth zone and controlling crystal nucleation by adding perforated graphite crystallization inserts and seed crystals to the growth zone (see a previous review [2]). Nevertheless, the principal drawbacks of this method have not been overcome. These include the high temperatures, the poor control of the nucleation, the small crystal sizes, the inability to control their shape (faceted plates grow), the inability to control production of various polytypes, and the uneven doping and dislocation distribution in the crystals grown. Therefore, alternative methods for growing silicon carbide crystals have been under development. A thermodynamic analysis of the growth of SiC single crystals from the melt demonstrated that the SiC melt itself can exist at temperatures greater than 3460 K and pressures greater than 104 MPa. This has not yet enabled the well-developed methods for growing crystals from their own melts to be used to prepare bulk SiC single crystals. Our investigations have revealed a low efficiency of the processes for growing bulk SiC single crystals from fluxes, a serious problem with the choice of crucible materials for holding the reaction melts, a substantial entrainment of solvent by the growing crystal, etc.

The thermodynamic analysis of high temperature processes in the SiC-N 2 system has been carried out at different initial pressures of nitrogen in the closed system 4, 200, 400, 600, 760, 1140 and 1520 Torr in the temperature interval (1500–3000) K. On the basis of thermodynamic analysis data it has been established that the stoichiometric relationship of silicon and carbon containing components in the vapour phase greatly depends on nitrogen pressure and temperature and this dependence is to be taken into account when analysing the phenomena of luminescence and polytypism in the course of growing silicon carbide monocrystals and epitaxial layers from the vapour phase. The “extent of development” of silicon carbide/nitrogen interaction reactions has been estimated and it has been shown that to certain temperatures (which depend on initial nitrogen pressure i P N 2 and shift toward higher temperatures under the increase of i P N 2 ) it is most likely the reaction, accompanied by the formation of liquid silicon and gaseous cyanogen.

The results of the study of SiC epitaxial layer growth kinetics in the system SiC-C are reported. The effects of temperature, pressure and heterogeneous reactions during the epitaxial layer formation have been studied in vacuum and at different partial pressures of argon in the system. An analysis of the experimental results was made on the basis of the theory of mass transfer by diffusion, taking into consideration the surface reactions. The dependence of the total supersaturation on the velocity of the epitaxial layer growth has been proposed. It has been established that above a certain pressures of argon in the system, and depending on the temperature of growth, the process is controlled primarily by mass transfer by diffusion, while at lower pressures the heterogeneous surface processes influence the kinetics of growth.

The concentrations of clusters of various size in the atmosphere during silicon carbide crystal growth have been calculated on the basis of fundamental ideas of homogeneous nucleation theory, taking into account the specific parameters of silicon carbide. It has been shown that the cluster concentration are sufficiently high to conclude that this is the dominant influence during the initial stages of crystal growth. In this way the assumption of the polymer theory of polytypism, namely that the polytype properties of silicon carbide can be determined from the composition of the gas phase, containing sufficiently large clusters with various polytype structures, has been confirmed.

A method to determine temperature gradient and distribution in high-temperature furnaces for silicon carbide monocrystal and epitaxial layer growing is suggested on the basis of the results obtained from the experiments on silicon carbide epitaxial layer growing kinetics in gas using 2 „sandwiches”. Russian Text Ignored.

As a result of investigation performed, the possibility of producing silicon carbide single-crystalline ingots grown from seeds in the 1800 to 2600°C range has been established. Silicon carbide single crystal growth in vacuum has been shown to be very promising at low temperatures.

The dependence of the smoothness of the crystallization boundary on the temperature gradient zone melting conditions is investigated. The observed depth of the crystallization boundary is compared with the depth, calculated by the method proposed by D. E. TEMKIN. [Russian Text Ignored].

Doping processes of silicon carbide crystals with scandium are investigated. It is shown that the scandium solubility in SiC is limited within the 1800 to 2600°C temperature range and amounts to (2 to 3) × 1017 cm−3. On doping silicon carbide crystals with scandium the VLS growth mechanism is possible. The luminescence spectra of the crystals are studied. It is found that nitrogen actively affects the luminescence intensity of silicon carbide doped with scandium. The depth of the radiative recombination centre in SiC (Sc) which is acceptor like is found to be 0.24 eV. [Russian Text Ignored].

The liquid phase epitaxy of SiC by the gradient temperature zone melting in the SiTb solvent is studied. A new variant of this growth method is presented. The comparison of the new variant with the previous one shows that the new variant allows for epitaxial layers with significant better electrophysical properties. It is easier and can be carried out at lower temperature. [Russian text Ignored]

In the present work the electrophysical and structural properties of the SiC epitaxial layers grown by the temperature gradient zone melting method in vacuum conditions is considered. Some correlations between the epitaxial layer properties and the process conditions are observed. It is shown that the performence of the growth process in vacuum leads to a significant improvement of the layer quality, if one observes some requirements – how to decrease significantly the number of the second phase inclusions and how to improve the structural perfection of the layers. [Russian Text Ignored].

The question of the interrelation of synthesis conditions with the energy distribution in photoluminescence spectra is studied for SiC epitaxial layers of 4H and 6H polytypes grown in the presence of rare-earth metals Tb and Sc. Marked differences in the energy distribution in the observed spectra indicate that in the process of growth from gas and liquid phases different emission centres are formed. It is found that the position of the maxima of the high temperature photoluminescence bands for 6H-SiC epilayers grown from the gas phase in the presence of Tb coincides with that for 6H-SiC layers in which boron is introduced by diffusion. [Russian text Ignored]

The paper summarizes the results of studies concerned with the processes of growing large silicon carbide single crystals of only one polytype. Vacuum sublimation has been found to be a suitable method of crystal growth. Mass-transfer aspects of crystal growth processes are analyzed, and the conditions of growing crystals of various polytypic structures are discussed. The as-grown crystals are suitable for the production of semiconductor devices.

In the paper which is divided into three parts the liquid phase epitaxy of SiC by temperature gradient zone melting with the solvent SiTb is discussed. In the first part the solubility of SiC at different initial compositions of the SiTb solvent is studied in the temperature range 2000–2500 K. [Russian text Ignored]

A qualitative dependence of polytype structures 6H, 15R, and 3C on the partial pressure of nitrogen in the interval 4 to 760 Torr is obtained by optical and X-ray studies of SiC epitaxial layers, grown by recrystallization in the gaseous phase at 1900 to 2300°C. The morphological peculiarities of β-SiC epitaxial layers, grown on the (0001) and (0001) faces of the α-SiC substrate are determined. The strained regions of the α-SiC monocrystals, due to inhomogeneous nitrogen-doping, are established by optical and X-ray methods. The effect of nitrogen on the polytype stability of SiC is the basis of the discussion of the experimental data. [Russian Text Ignored]

Recombination centres in luminescent crystals n-SiC(6H) doped with nitrogen and compensated with boron during the diffusion process are investigated by photocapacitance method. Boron diffusion results in appearance of a deep centre which is able to capture holes effectively. The ionization energy of this centre ET = (0.4 ± 0.02) eV coincides with the boron ionization energy in p-SiC(6H): B crystals and the spectral dependence of photoionization cross-section qp is similar to the spectral dependence of absorption near the long-wave edge of the absorption band of these crystals. But such centre is not observed in n-SiC(6H): B original samples in spite of the large quantity of boron in them. Based on these facts the conclusion can be made that boron with respect to the capture of the holes may be either in active or in bound states depending on the method of doping. This results in different efficiency of photoluminescence of crystals doped with boron in the growth and diffusion processes. [Russian Text Ignored].

The kinetics of silicon carbide synthesis plays an important part in the formation of polytypes during the growth of crystals and epitaxial layers. The results obtained permit to develop a technique of plotting kinetic phase diagrams with the polytypes shown for silicon carbide. In particular, these phase diagrams accomodate quite well the conditions of production (rather high growth rates at comparatively low temperatures of growing) of crystals and epitaxial layers of β-SiC from solutions in silicon melts and at decomposition in hydrogen of methyl-trichlorosilane and other silicon-and carbon-containing organic compounds. [Russian text Ignored.]

A thermodynamic analysis of the equilibrium in the SiC-H2 system has been carried out at various constant pressures (1, 5 × 10-1, and 10-2 atm) over the 1500–3000 K temperature range. On the basis of thermodynamic analysis data it has been established that the stoichiometric relationship of the silicon- and carbon-containing components in the vapour phase greatly depends on the hydrogen temperature and pressure. This dependence is to be taken into account when analysing the processes of diffusion mass-transfer and heterogeneous interactions in the course of growing silicon carbide epitaxial layers. “The extent of development” of silicon carbide-hydrogen interactions has been estimated, and it has been found that for all H2 pressures studied in the 1850–2350 K temperature range, the reaction accompanied by the formation of gaseous silicon and C2H2 is the most likely.

The growth kinetics of silicon carbide epitaxial layers from the vapour phase using the “sandwich” method has been investigated and the limiting stages of the growth process have been established as a function of the argon pressure in the growth zone. The methods of determining the temperature gradient and its distribution in the high-temperature furnaces have been developed. On the basis of analysis of mass transfer efficiency and kinetics as well as the calculations of vapour pressures in the temperature change of 1800–3000 K, it has been shown that silicon in the vapour phase acts as a “transporting agent” during the growth of silicon carbide crystals and epitaxial layers.

Silicon carbide epitaxial layers were grown from the vapour phase at 2050–2500 K by the sublimation technique. Films 0.02-0.1 mm thick have been grown. It is found that in the 2320–2420 K range the conditions stabilizing film growth of 6H-SiC polytype are realized independently of substrate polytype. Excessive donor concentration in the growth layers amounted to (2–10) × 10 17 cm -3 with the degree of compensation as high as 50%.

The present paper gives results of sublimation growth studies of SiC crystals. From these results one can conclude that the vapour-liquid-solid (VLS) growth mechanism as well as the vapour-solid (VS) mechanism is possible for SiC crystals grown by the sublimation method. For the studies of SiC crystals grown by the sublimation method the authors have prepared pure single crystals as well as crystals doped with nitrogen, boron, aluminium, beryllium, scandium, and lanthanum.

Synthesis, study and application of increasingly more complex crystalline structures are one of the most important tendencies in physics and the science of materials of solid-state electronics. The creation of A3B5 compounds and multi-component solid solutions based on these compounds, superlattices, complex ceramic high-temperature superconductors and other materials made it possible to enlarge substantially the possibilities of solid-state electronics, to create devices with wider ranges of operating characteristics and functional possibilities.

Polytypic crystals of semiconductors, dielectrics and magnetic materials attract an increasing attention in science and technology. On one hand, the phenomenon of polytypism is one of the fundamental problems of solid-state physics; its solution would make it possible to elucidate- the problem of the interconnection of different structures and intraatomic forces acting in crystals. On the other hand, the polytypic difference in crystals is most strongly expressed in electro-physical properties, which makes their application promising, mainly in semiconductor electronics. Thus, the difficulties of producing modulated structures in polytypic crystals can be overcome since these crystals form a class of one-dimensional natural superlattices.