We report on the fabrication of nonpolar GaN(11‒20) structures by hydride vapor phase epitaxy using an AlN buffer layer synthesized by metalorganic vapor-phase epitaxy on an r-Al2O3 substrate. It is shown that the elastic stresses in the GaN(11‒20)/r-Al2O3 structure in the directions of the c and a axes of the layer have different values, correlate with the full widths at half maximum of the rocking curves in the X-ray diffraction spectra in these directions, and are caused by the anisotropy of the thermal expansion coefficients of the layer and substrate lattices.

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.

It has been reported the growth of nonpolar GaN(11 ̄20) structures by hydride vapor phase epitaxy, which used an AlN buffer layer synthesized by epitaxy from organometallic compounds on an r-Al2O3 substrate. It has been shown that the elastic stresses in the GaN(11 ̄20)/r-Al2O3 structure in the direction of the ”c“and ”a“axes of the layer differ, correlate with the values of the full width at half maximum of the X-ray diffraction spectra in these directions and are due to the anisotropy of the thermal expansion coefficients of the lattice, both the layer and the substrate.

Results of an epitaxial growth of 3C-SiC epilayers on hexagonal 6H-SiC, 4H-SiC substrates are described. The study of the obtained epitaxial layers grown on 6H substrates was made by photoluminescence and optical microscopy. Also, an image analysis of the interface of 3C-SiC epitaxial layers with 6H, 4H, and 15R substrates obtained by Transmission Electron Microscopy (TEM) are presented. Difference between the layers on the Si and C faces are discussed.

Photoluminescence (PL) spectra have been studied in 3C-SiC/4H-SiC heterostructures and 3C‑SiC single crystals. It was shown that epitaxial 3C-SiC layers grown on 4H-SiC substrates have a markedly poorer crystal perfection than do 3C-SiC single crystals. It was found that doping with aluminum gives rise to a characteristic PL both in epitaxial layers and in 3C-SiC single crystals. At the same time, the electron irradiation of epitaxial layers does not give rise to defect-related PL, in contrast to what is observed for single crystals. An assumption is made that the twin boundaries existing in epitaxial 3C-SiC layers can serve as getters of radiation defects that are components of donor–acceptor pairs responsible for the “defect-related” PL.

AbstractSemipolar GaN layers synthesized on a nanostructured Si(100) substrate are studied. It is shown that using a Si(100) nanoprofile combined with Si_ x N_ y 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 ω_θ ≈ 35′ arcmin. It is found that the luminescence properties of the semipolar layers are mostly due to basal plane stacking faults BSF_ S -I_1, in contrast to polar layers in which these properties are mostly due to the recombination of excitons.

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.

AbstractPhotoluminescence (PL) spectra have been studied in 3 C -SiC/4 H -SiC heterostructures and 3 C ‑SiC single crystals. It was shown that epitaxial 3 C -SiC layers grown on 4 H -SiC substrates have a markedly poorer crystal perfection than do 3 C -SiC single crystals. It was found that doping with aluminum gives rise to a characteristic PL both in epitaxial layers and in 3 C -SiC single crystals. At the same time, the electron irradiation of epitaxial layers does not give rise to defect-related PL, in contrast to what is observed for single crystals. An assumption is made that the twin boundaries existing in epitaxial 3 C -SiC layers can serve as getters of radiation defects that are components of donor–acceptor pairs responsible for the “defect-related” PL.

Исследовано воздействие протонного облучения с энергией 8 МэВ на эпитаксиальные слои n-3C-SiC, выращенные методом сублимации на полуизолирующих подложках 4H-SiC. Изменения параметров образцов регистрировали методом эффекта Холла и по спектрам фотолюминесценции. Метод Холла был применен для раздельной оценки влияния облучения на концентрацию и подвижность носителей заряда. Скорость удаления носителей (Vd) составила ~110 см-1. Полная компенсация образцов с исходной концентрацией носителей заряда 6.5·1017 см-3 наблюдалась при дозах облучения ~6·1015 см-2. Подвижность носителей заряда при таких дозах облучения уменьшалась всего в 2.5 раза. По сравнению с 4H и 6H карбида кремния не было отмечено значительного увеличения интенсивности так называемой "дефектной" фотолюминесценции. DOI: 10.21883/FTP.2017.08.44795.8535

Effects of proton irradiation in n-3C-SiC grown by sublimation on a 4H-SiC substrate have been studied by the Hall effect and photoluminescence methods. It was found that the carrier removal rate (Vd) reaches a value of ~110 cm-1. The full compensation of samples with an initial concentration of (1-2) x 1018 cm -3 was estimated to occur at doses of about 6 x 1015 cm -2. Compared with 4H and 6H silicon carbide, no significant increase in the intensity of so-called "defective" photoluminescence was observed in 3C-SiC.

The effects of 8-MeV proton irradiation on n-3C-SiC epitaxial layers grown by sublimation on semi-insulating 4H-SiC substrates are studied. Changes in the sample parameters were recorded by the Hall-effect method and judged from photoluminescence spectra. The Hall method was employed to distinguish between the effects of irradiation on the charge-carrier concentration and mobility. It is found that the charge-carrier removal rate (V d ) is ~110 cm–1. Full compensation of the samples with an initial charge-carrier concentration of ~6.5 × 1017 cm–3 is observed at irradiation doses of ~6 × 1015 cm–2. It is found that the mobility at these doses decreased by only a factor of 2.5. Compared with 4H and 6H silicon carbide, no significant increase in the intensity of so-called defect-related photoluminescence is observed.

By now we know almost nothing about works on production of p-3C-SiC. Probably, it is due to the fact that the basic acceptor impurity (aluminium) accumulates on the interfaces of the twins and other structural defects in the 3C film and it is electrically neutral. We managed to produce the highly doped layers p-3C based on the conducting substrates of hexagonal SiC using the method of Sublimation Epitaxy (SE). Probably, it is due to the growth high temperature used in this method. First, it results in production of the more structural-perfect epifilm and, second, in increasing the Al atomic mobility. This works purpose is further optimization of the production technology for epilayers p-3C-SiC with usage of semi-insulating substrates 6H-SiC.

In the article we report on results of epitaxial growth of GaN on Si substrate in the new HVPE reactor. The reactor was designed for growth of GaN on substrates with diameter up to 76 mm. Thin layer of AlN were deposited in MOCVD reactor in order to prevent reaction between Ga and Si. 10-micron-thickness flat GaN layers were fabricated on MOCVD AlN/Si by HVPE. The GaN layers were characterized by PL, XRD, SEM and mercury probe. The FWHM of XRD rocking curves for GaN peak (0002) was about 500 arcsec, that is similar for the best samples MOCVD GaN/Si.

The photoluminescence (PL) arising in low doped CVD grown n- and p-type 4H-SiC upon electron irradiation (0,9 MeV) has been studied. After each doze of irradiation spectrum of PL was measured. The PL spectrum was dominated by a band peaked at hv approximate to 2,45 eV, commonly observed upon irradiation of SiC. The experiments demonstrated that, for samples with both types of conduction, the PL intensity approaches a constant value with increasing irradiation dose. A model was suggested, describing the PL characteristics in terms of the radiative recombination via a donor-acceptor pair constituted by nitrogen and a structural defect formed in the course of irradiation. Also, the concentration of nitrogen atoms was measured by the SIMS method. The experimental data were used to calculate in terms of the suggested model the dependence of the PL intensity on the irradiation dose. A good agreement between the calculated and experimental dependences was observed. A conclusion is made that the PL is activated by donor-acceptor pairs constituted by a nitrogen atom and a structural defect.

Photoluminescence (PL) appearing in p-4H-SiC upon its electron irradiation has been studied. A model that accounts for the dependence of the PL intensity on the irradiation dose is suggested. The conclusion is drawn that nitrogen–radiation defect donor–acceptor pairs are PL activators.

The compensation of moderately doped p-4H-SiC samples grown by the chemical vapor deposition (CVD) method under irradiation with 0.9-MeV electrons and 15-MeV protons is studied. The experimentally measured carrier removal rates are 1.2–1.6 cm–1 for electrons and 240–260 cm–1 for protons. The dependence of the concentration of uncompensated acceptors and donors, measured in the study, demonstrates a linear decrease with increasing irradiation dose to the point of complete compensation. This run of the dependence shows that compensation of the samples is due to the transition of carriers to deep centers formed by primary radiation-induced defects. It is demonstrated that, in contrast to n-SiC (CVD), primary defects in the carbon sublattice of moderately doped p-SiC (CVD) only cannot account for the compensation process. In p-SiC, either primary defects in the silicon sublattice, or defects in both sublattices are responsible for conductivity compensation. Also, photoluminescence spectra are examined in relation to the irradiation dose.

Effects of electron irradiation in n-4H-SiC have been studied by the methods of the capacitance--voltage characteristics and photoluminescence. It was found that the carrier removal rate (Vd) reached a value of ~0, 25 cm - 1 . Full compensation of samples with an initial concentration of 1.2 10 15 cm -3 was observed at doses of about 5 10 15 cm -2 . Simultaneously with the increase in the degree of compensation, the intensity of the “defect luminescence”, typical of 4H SiC, became higher. The physical compensation mechanisms were analyzed for the samples under study.

Abstract Results of an epitaxial growth of 3C-SiC epilayers on Si (0001) and C(000¯1) faces of hexagonal 6H-SiC substrates are described. TEM study of grown layers as well as interface between cubic and hexagonal polytypes is presented. Difference between the layers on the Si and C faces are discussed.

It is demonstrated that polytype-homogeneous, thick (>100 m) epitaxial 3C-SiC layers of good quality with diameters of no less than 25 mm can be grown on 6H-SiC substrates by sublimation epitaxy in vacuum. These layers can be used as seeds for growing bulk 3C-SiC crystals by modified Lely method.

It is demonstrated that polytype-homogeneous, thick (>100 μm) epitaxial 3C-SiC layers of good structural quality with diameters of no less than 25 mm can be grown on 6H-SiC substrates by sublimation epitaxy in vacuum. These layers can be used as seeds for growing volume 3C-SiC crystals by the modified Lely method.