N. V. Seredova

Effect of irradiation with MeV protons and electrons on the conductivity compensation and photoluminescence of moderately doped p-4H-SiC (CVD)

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.

Radiation-stimulated photoluminescence in electron irradiated 4H-SiC

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 ≈ 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.

Heteroepitaxial Growth of 3C-SiC on Polar Faces of 6H-SiC Substrates, TEM Investigations

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.

On Application of Sublimation Epitaxy to Growth of Bulk 3C-SiC Crystals

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.

Study of the 3C-SiC layers grown on the 15R-SiC substrates

The 3C-SiC layers grown on the 15R-SiC substrates by sublimation epitaxy in vacuum are studied. Using X-ray topography and Raman spectroscopy, it is shown that the obtained layers are of a rather high structural quality. By the data of the Raman spectroscopy and capacitance-voltage measurements, it is established that the electron concentration in the 3C-SiC layer is (4–6) × 1018 cm−3.

Luminescent properties of GaN-based epitaxial layers and heterostructures grown on porous SiC substrates

The photoluminescence of single epitaxial GaN layers and electroluminescence of double GaN/AlGaN heterostructures grown on porous silicon carbide (PSC) substrates was studied in comparison to the properties of analogous layers and structures grown on nonporous SiC substrates. The epilayers grown on PSC substrates are characterized by a lower concentration of dislocation-related nonradiative recombination centers. It is suggested that this factor favorably influences the radiative recombination processes in device structures based on group III nitride epilayers grown on PSC substrates.

Electrical properties of n-GaN/p-SiC heterojunctions

Epitaxial GaN layers were grown by hydride vapor phase epitaxy (HVPE) on commercial (CREE Inc., USA) p+-6H-SiC substrates (Na − Nd ≈ 7.8 × 1017 cms−3) and n+-6H-SiC Lely substrates with a predeposited p+-6H-SiC layer. A study of the electrical properties of the n-GaN/p-SiC heterostructures obtained confirmed their fairly good quality and demonstrated that the given combination of growth techniques is promising for fabrication of bipolar and FET transistors based on the n-GaN/p-SiC heterojunctions.

Effects of irradiation with 8-MeV protons on n -3 C -SiC heteroepitaxial layers

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 (Vd) 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.

On the relationship between radiation-stimulated photoluminescence and nitrogen atoms in p-4H-SiC

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.

Use of sublimation epitaxy for obtaining volume 3C-SiC crystals

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.