Single-crystalline α-Cr 2 O 3 layers were synthesized on a sapphire substrate with a basal orientation in a laboratory reactor using ultrasonic-assisted chemical vapor deposition in the temperature range of 700-850 o C. The influence of the growth temperature on the structural quality of the layer was studied by X-ray diffraction. At a growth temperature of 800 o C, continuous layers with a thickness of about 1 μm were obtained. The layers were transparent in the visible region with a slightly greenish tint and showed some light transmission up to wavelengths of ~ 350 nm. The full width at half maximum of the rocking curve for reflection 0006 was ~ 300 arcsec. Keywords: chromium oxide, CVD epitaxy, wide-bandgap semiconductor.

In the article, using the example of growing aluminum nitride (AlN) on (110) orientation silicon (Si) with a silicon carbide (SiC) buffer layer, a method for growing a new type of substrates is developed which makes it possible to obtain mechanically unstressed semiconductor heterostructures. A specific feature of the synthesis of this kind of substrates is that the SiC layers used for the growth of AlN films were synthesized by the coordinated atoms substitution method. When this method of growth is used in the Si substrate, some of the Si atoms are replaced by carbon atoms. As a result of the substitution of atoms, the initially smooth Si(110) surface transforms into a SiC surface covered with prism-like growth figures, one side of which is the (111) face and the other is the (111̅) face. These faces are “substrates” for the further growth of semipolar AlN. The structure and morphology of AlN films have been studied by X-ray diffraction, electron microscopy, and Raman spectroscopy. It was found that the AlN layer is formed by intergrown hexagonal microcrystals, which grow in two directions, and for both orientations of the crystals the following relation is approximately satisfied: AlN ( 101̅3) ||Si(110). It is shown that the half-width of the X-ray rocking curve (FWHM) for the diffraction peak from AlN microcrystals, averaged over the area of the sample, is 20 arc minutes. Raman spectroscopy and X-ray diffraction studies have shown the almost complete absence of mechanical stresses in the AlN layer. A theoretical model is constructed to explain the presence of two orientations of the AlN film on SiC/Si(110) found in the experiment, and a method for controlling their orientation is proposed. It is shown that this morphology of the AlN film makes it possible to use it as a buffer layer for the growth of heterostructures based on gallium nitride and aluminum nitride.

Record thick (up to 100 μm) epitaxial layers of a prospective semiconductor metastable Ga2O3 were grown by HVPE (Halide Vapor Phase Epitaxy) on GaN buffer layers on c-sapphire substrate. The X-ray diffraction spectra of the layers show that the structure of the layer is a pure k(ε)-Ga2O3 without any other phases. At the same time, the organization of the domain structure is noted, which manifests itself in the form of pseudohexagonal prisms with the inheritance of the orientation of the gallium nitride sublayer. Schottky diodes with a nickel contact were fabricated and the electrical and photoelectric properties of the layers were studied. Capacitance-voltage (C-V) and frequency-capacitance (C-f) dependencies have been studied, photocurrent and photocapacitance spectra have been measured.

The effect of H2, NH3, CO and O2 on the electrically conductive properties of In2O3 films grown by halide vapor phase epitaxy has been studied. In the temperature range of 200−550°C, In2O3 films demonstrate gas sensitivity to all considered gases, a relatively high operation speed and repeatability of cycles. The greatest response to NH3 was obtained, which exceeded 33 arb.units at a temperature of 400°C and a gas concentration of 1000 ppm. A qualitative mechanism of gas sensitivity of In2O3 films is proposed. The obtained gas-sensitive characteristics are compared with known NH3 sensors based on various materials. It is shown that the method of halide vapor phase epitaxy makes it possible to obtain indium oxide films with high gas sensitivity

Single-crystalline α-Cr2O3 layers were synthesized on a sapphire substrate with a basal orientation in a laboratory reactor using ultrasonic-assisted chemical vapor deposition in the temperature range of 700-850°C. The influence of the growth temperature on the structural quality of the layer was studied by X-ray diffraction. At a growth temperature of 800°C, continuous layers with a thickness of about 1 μm were obtained. The layers were transparent in the visible region with a slightly greenish tint and showed some light transmission up to wavelengths of ~350 nm. The full width at half maximum of the rocking curve for reflection 0006 was ~ 300 arcsec.

Сообщается о росте неполярных GaN(1120) структур методом хлорид-гидридной газофазной эпитаксии с использованием буферного слоя AlN, синтезированного методом эпитаксии из металлоорганических соединений на подложке r-Al2O3. Показано, что упругие напряжения в структуре GaN(1120)/r-Al2O3 в направлении осей "c" и "a" слоя различаются, коррелируют с величинами полуширин кривых качания спектров рентгеновской дифракции в этих направлениях и обусловлены анизотропией коэффициентов термического расширения решеток как слоя, так и подложки. Ключевые слова: неполярный нитрид алюминия, анизотропия напряжений в слое.

α-Ga2O3/α-Cr2O3 heterostructures with a corundum structure were obtained by chloride vapor phase epitaxy and magnetron sputtering. The structural, electrical conductive and photoelectrical properties of the obtained samples were studied. It was established that the α-Ga2O3/α-Cr2O3 heterostructures exhibits weak rectifying properties and in comparison with α-Ga2O3 films has a higher response speed when exposed to ultraviolet radiation.

High crystalline quality epitaxial films of orthorhombic gallium oxide ε(κ)-Ga2O3 with a thickness of more than 20 μm have been grown by halide vapor phase epitaxy for the first time. Sapphire wafers with preliminarily deposited GaN layers were used as substrates. The properties of the produced films are studied by X-ray diffraction and electron microscopy. The results obtained are considered as an important step in obtaining thick layers and quasi-bulk ε(κ)-Ga2O3 crystals for practical applications in electronic and sensor technology.

The effect of the gaseous medium composition on the electrically conductive properties of In2O3-Ga2O3 films obtained by chloride vapor phase epitaxy has been studied. In the temperature range of 100-550ºC the In2O3 -Ga2O3 films exhibit high sensitivity to H2, NH3 and CO possessing high-speed performance and low-base-resistance. A qualitative mechanism for the sensitivity of In2O3-Ga2O3 films to gases is proposed.

The work is devoted to the study of p-GaN: Mg epitaxial layers grown by the ammonia MBE technique. We find that the conductivity of GaN layers doped with Mg does not change with a postgrowth heat treatment. Formation of Mg3N2 nanocrystallites on GaN surface during epitaxial growth of the GaN layer with a high magnesium doping level was detected by the RHEED technique for the first time. It was shown that the Mg3N2 nanocrystallites formation competes with the acceptor states formation process. It has been proposed that the growth temperature can be applied as an additional “tuning” mechanism which affects the Mg incorporation into the growing GaN:Mg layers.

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 AlN were grown on a Si(111) substrate using several sequential methods: reactive magnetron sputtering (up to a thickness of 20 nm), MOCVD (up to a thickness of 450 nm), and HVPE (up to a thickness of 2 microns).The formation of AlN by this combined method provides a significant reduction in layer deformation and suppression of crack formation.

Epitaxial layers of a new wide-band semiconductor (α-Ga 2 O 3 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-Ga 2 O 3 layers on smooth and patterned substrates have been identified by X-ray diffractometry.

4 H -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.

Abstract Epitaxial layers of a new wide-band semiconductor (α-Ga_2O_3 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-Ga_2O_3 layers on smooth and patterned substrates have been identified by X-ray diffractometry.

The photoluminescent properties at 77 and 300 K are investigated for Ga1 xInxAsyP1 y epilayers with V-group elements content gradient Δy up to 0.08 across whole thickness (about 1 µm). Ga1 xInxAsyP1 y layers with high Δy values have widened photoluminescence spectra. For GaInAsP layers of low crystaline perfection, photoluminescence was either absent or manifested itself as it is typical for transitions involving impurity levels.

GaInPAs/InP heterostructures grown by low pressure (0.1 bar, 600 oC) metal-organic chemical vapor phase deposition were investigated. The thicknesses of grown GaInAsP layers were about 1 µm. For the epitaxial layers Ga1-xInxP1-yAsy) with average compositions of x = 0.77 – 0.87 and y = 0.07 – 0.42 the variation of V group elements content y with the epilayer depth were revealed, weher the compositions of V-group elements were changed up to Δy = 0.1 atomic fractions in V group elements sublattice. In most cases, y change occurs in a GaInAsP region up to 200 nm thick adjacent to the InP. In some cases, y changes throughout the whole GaInPAs layer thickness. Fo the epitaxial layers with a satisfactory crystal perfection the less was the mismatch between the substrate and the GaInPAs epitaxial layer, the smaller was the value of Δy. For GaInPAs layers characterized by a low degree of crystal perfection and a high lattice mismatch between GaInAsP and InP layers, the value of Δy was about zero. These data let us suggest that the incorporation of atoms of the V group in the epitaxial layer strongly depends on elastic deformation of the growing monolayer, that is mismatched with the underlying crystal surface.

AbstractElectric polarization in ErCrO_3 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. These temperatures correspond to the condition kT _fr ≈ E _A for activation barriers at the boundaries of the restricted polar domains.