Papers by Author: N.S. Savkina

Abstract: We present the injection electroluminescence spectra in the temperature range 290-760 K of 3C-SiC pn structure, which was fabricated by sublimation epitaxy in vacuum on 6H-SiC substrate. The dominant emission band of injection electroluminescence (IEL) spectrum was observed in the green region; at room temperature the IEL intensity outside the region of hν ≈ 2.0- 2.5 eV was less than 3% of that of the green peak. The peak parameters at room temperature are: hνmax ≈ 2.32 eV, full width at half maximum w ≈ 100 meV. The green peak shifted in the longwave direction with increasing temperature; the hνmax (T) dependence was linear with the slope of - 1.3x10-4 eV/K. Both the IEL intensity of the green peak at hνmax and band width w increased upon heating. The w(T) dependence was linear with the slope of 4.6x10-4 eV/K; intensity increased with the activation energy of 70 meV. The green IEL band can be considered to be due to the free exciton annihilation or to the band-band recombination and edge IEL increasing with rising temperature can be explained by the nonequilibrium charge carriers lifetime increasing.

Abstract: Nuclear-particle detectors based on SiC with a structure composed of an n+-type substrate, a p-type epitaxial layer, and a Schottky barrier are studied. Structures with a ~10-µm-thick 6H-SiC layer exhibit transistor properties, whereas those with a ~30-µm-thick 4H-SiC layer exhibit diode properties. It is established that a more than tenfold amplification of the signal is observed in the transistor-type structure. The amplification is retained after irradiation with 8-MeV protons with a dose of at least 5 × 10 13 cm –2 ; in this case, the resolution is ≤ 10%. Amplification of the signal was not observed in the structures of diode type. However, there were diode-type detectors with a resolution of ≈ 3%, which is acceptable for a number of applications, even after irradiation with the highest dose of 2 × 10 14 cm.

Abstract: The methods of X-ray topography and diffractometry have been applied to characterize the structure of epilayers grown on porous layers. Two geometrical configurations of defects determined to be stacking faults (SF) were revealed: i) with the images of triangular shape with the edge size 560 µm along the <10-10> directions; ii) linear shape along the [11-20] direction. The sources of SFs are located within the epilayer and start from the epilayer / porous layer interface. We propose that the source of SFs is connected with graphitization of porous layer at the temperature of epitaxy.

Abstract: We have studied effects of thermal treatment in vacuum and wet oxidation on the optical transmission of SiC samples with porous layer on the Si face in the visible and near infrared spectral range. An analysis of changes in the absorption coefficient shows that the process of graphitization in vacuum begins at a temperature below 700°C and can be observed at wet oxidation at 1000°C.