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The mechanism of structure transformation in Cr/4H–SiC UV photo detectors, which is responsi-ble for the cyclic gettering of radiation defects, under repeated proton irradiation, is proposed in this work. [ABSTRACT FROM AUTHOR]

The results of the effect of irradiation with Ar ions on the structural, electrophysical, and optical characteristics of ultraviolet Cr/4H-SiC photodetectors in the spectral range 200 to 400 nm are presented. After a single irradiation with Ar ions with an energy of 53 MeV with a fluence of 1 × 1010 cm–2 the values of the quantum efficiency of photodetectors practically remain at the level of the initial samples due to the "gettering effect" of simple radiation defects by cluster formations. This effect contributes to a decrease in the number of simple radiation defects of the vacancy type, an increase in the lifetime of current carriers, and, as a result, unchanged values of the photoconductivity of Cr/4H-SiC photodetectors. After the repeated irradiation of photodetectors with Ar ions with a total fluence of 2 × 1010 cm–2 the decay of clusters and the formation of a significant number of simple defect centers are observed, which lead to a decrease in the lifetime of the current carriers and photoconductivity of Cr/4H-SiC detectors. [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]