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An approach of direct bonding of SiC wafers of differing polytypes has been implemented in order to create a template for cubic 3C-SiC homo epitaxy. Hetero epitaxial 3C-SiC layers grown by chemical vapor deposition were transferred onto a hexagonal 6H-SiC wafer. The results of structural characterization showed that the quality of 3C-SiC sublimation epitaxy on the templates is comparable to the level of epitaxy of cubic silicon carbide by chemical vapor deposition method. It was confirmed that the 3C-SiC layer transferred onto the 6H-SiC substrate plays the role of a crystalline "seed" that determines cubic polytype of the overgrown SiC layer. [ABSTRACT FROM AUTHOR]

Heavily doped 3C-SiC films based on semi-insulating 6H-SiC substrates were obtained by sublimation epitaxy. The structural perfection of the obtained samples was monitored by X-ray diffractometry. The measurements of the photoluminescence and Hall effect spectra have confirmed the rather high perfection of the obtained epitaxial layers. [ABSTRACT FROM AUTHOR]

The results of investigations of initial n-4H–SiC structures by various methods are presented. The structures represent a highly doped n+ substrate with epitaxial layers 5 μm thick grown by chemical vapor deposition (CVD). The concentration of uncompensated donors in the epitaxial layer is in the range of Nd – Na = (1–50) × 1014 cm–3. Using the results of X-ray diffraction analysis, it is found that, in order to obtain efficient 4H–SiC ultraviolet photodetectors, it is desirable to have structures of epitaxial layers in which the effect of point-defect gettering, leading to an increase in the lifetime of charge carriers and in the values of quantum efficiency, is observed. The photosensitivity of the investigated samples significantly depends on the degree of imperfection of the CVD epitaxial layer, which results in a change in the lifetime of charge carriers and, as a consequence, in a change in the quantum efficiency of 4H–SiC ultraviolet photodetectors. [ABSTRACT FROM AUTHOR]

The influence exerted by the carrier concentration in the range (1–50) × 1014 cm–3 in n-4H-SiC chemical-vapor deposited (CVD) epitaxial layers on the spectral characteristics of UV photodetectors with Cr Schottky barriers in the range of 200–400 nm is revealed and explained in terms of the photoconductivity theory. Schottky barriers with a Cr film thickness of 20 nm and diameter of 8 mm are formed by thermal evaporation in vacuum through masks. A noticeable effect of the carrier concentration in the CVD epitaxial layers on the spectral characteristics of photodetectors upon heating to 200°C is also observed and accounted for by a difference between the generation-recombination processes. The irradiation of photodetectors with 15-MeV protons at a fluence of 4 × 1012 cm–2 and a temperature of 200°C leads to an increase in the quantum efficiency as compared to samples irradiated in similar modes at 25°C. This is indicative of an increase in the radiation hardness and service life of 4H-SiC devices at elevated temperatures. [ABSTRACT FROM AUTHOR]

For the first time, comprehensive comparative investigations of ultraviolet photodetectors with Cr Schottky barriers formed on 4H-SiC epitaxial layers are carried out by the X-ray and optical methods before and after irradiation with 15-MeV protons with fluences in the range of (1–4) × 1012 cm–2. When increasing the fluence of proton irradiation, the formation of localized regions with negative deformation is observed along with the unperturbed silicon-carbide matrix. Agreement between the X-ray and optical studies is obtained, which makes it possible to explain the features of the spectral changes in the photosensitivity of detectors in the range of 200–400 nm with an increase in the fluence of proton irradiation. The ultraviolet Cr/4H-SiC photodetectors withstand irradiation by 15-MeV protons with a fluence of 4 × 1012 cm–2 virtually without any changes in the photosensitivity due to the gettering of simple defects by cluster and amorphous formations, which lead to partial structural improvement of the irradiated material. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]