P. L. Abramov

Highly doped p-type 3C–SiC on 6H–SiC substrates

Highly doped p-3C-SiC layers of good crystal perfection have been grown by sublimation epitaxy in vacuum. Analysis of the photoluminescence spectra and temperature dependence of the carrier concentration shows that at least two types of acceptor centers at ∼EV + 0.25 eV and at EV + 0.06-0.07 eV exist in the samples studied. A conclusion is reached that layers of this kind can be used as p-emitters in 3C-SiC devices.

A study of thick 3C-SiC epitaxial layers grown on 6H-SiC substrates by sublimation epitaxy in vacuum

Abstract3C-SiC epitaxial layers with a thickness of up to 100 µm were grown on 6H-SiC hexagonal substrates by sublimation epitaxy in vacuum. The n-type epitaxial layers with the area in the range 0.3–0.5 cm2 and uncompensated donor concentration Nd − Na ∼ (1017–1018) cm−3 were produced at maximum growth rates of up to 200 µm/h. An X-ray analysis demonstrated that the epitaxial layers are composed of the 3C-SiC polytype, without inclusions of other polytypes. The photoluminescence (PL) spectrum of the layers was found to be dominated by the donor-acceptor (Al-N) recombination band peaked at hv ≈ 2.12 eV. The PL spectrum measured at 6 K was analyzed in detail. It is concluded that the epitaxial layers obtained can serve as substrates for 3C-SiC-based electronic devices.

Metal-insulator transition in n-3C-SiC epitaxial films

The paper reports a study of galvanomagnetic properties of n-3C-SiC/n-6H-SiC heterostructures at liquid-helium temperatures. 3C-SiC epitaxial layers were grown by sublimation epitaxy in a vacuum on the (0001)C face of 6H-SiC substrates produced by the Lely method and 4H-SiC substrates grown by modified Lely method. The x-ray topography demonstrated the high quality structure of the epitaxial layers and the absence of any transition regions between 3C-SiC epitaxial layer and substrate. The low-temperature conductivity and magnetoresistance of the films have been studied as functions of their doping level and structural quality. It was found that the metal-insulator transition occurs in the n-3C-SiC layer at concentrations Nd−Na≤3×1017 cm−3.

Peculiarities of impact ionization of Impurity Al in SiC polytypes

The specific character of impact ionization of a small radius impurities was investigated in polytypes 6H-, 4H-, and 15R-SiC. The I-V characteristics of Al breakdown in 6H-, 4H-, and 15R-SiC in electrical field were studied. It was shown that at 77 K the impurity breakdown takes place only under the large impurity concentrations (three orders larger than that in Ge). The following data were obtained: the decreasing dependence of breakdown field due to the concentration increase, the absence of the low temperature breakdown at low impurity concentration, and gigantic enhancement of breakdown field when the field is parallel to the crystal axis.

Studying 3C-SiC epilayers grown on the (0001)C face of 6H-SiC substrates

Epitaxial 3C-SiC films grown on the (0001)C face of 6H-SiC substrates by sublimation epitaxy in vacuum have been studied. The results of x-ray diffraction measurements show evidence of a rather high structural perfection of silicon carbide epilayers. The Raman spectroscopy data confirm that the 3C-SiC layer grows immediately on the 6H-SiC substrate without any transition layers. It is concluded that the structures under consideration are well suited for the investigation of a two-dimensional electron gas at the 3C-SiC/6C-SiC heterojunction

Growth and Study of Thick 3C-SiC Epitaxial Layers Produced by Epitaxy on 6H-SiC Substrates

3C-SiC epitaxial layers with a thickness of up to 100 μm and area of ~0.3-0.5 cm2 have been grown by sublimation epitaxy on hexagonal (6H-SiC) substrates at a maximum growth rate of about 200 μm per hour. The epilayers obtained are of n-type (Nd-Na ~ 1017 -1018 cm-3). According to X-ray data, the epitaxial layers are composed of the 3C-SiC polytype, without inclusions of other polytypes. The donor-acceptor (Al-N) recombination band with hνmax ~ 2.12 eV predominates in the photoluminescence (PL) spectrum. A detailed analysis of a PL spectrum measured at 6 K is presented. A conclusion is made that the epitaxial layers can be used as substrates for electronic devices based on 3C-SiC.

Fabrication of improved-quality seed crystals for growth of bulk silicon carbide

Sublimation epitaxy in a vacuum has been used to grow silicon carbide layers with a low defect concentration and with SiC wafers cut from single-crystal ingots produced by the modified Lely method serving as substrates. It is concluded on the basis of a comparative study of the distribution of structural defects in substrates and epitaxial layers that an isomorphic pair composed of an epitaxial layer and a single-crystal SiC substrate, which is a composite of materials produced by the same method (sublimation synthesis), but in different technological conditions, is promising for fabrication of improved-quality silicon carbide seed crystals.

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.

The Strong Field Transport in 4H- and 6H-SiC at Low Temperature

A natural superlattice (NSL) in silicon carbide polytypes is shown to introduce a miniband structure into the conduction band, which leads to depressing of the electron impact zone-zone ionization at 300K with the electric field directed along the crystal axis or the NSL axis. The NSL influence can be also observed in the nitrogen impact ionization at 4.2K. In this case for the parallel field the impurity breakdown has not been fixed up to the fields 1.6 MV/cm in 6H-SiC. These results are explained by the insufficient gain in miniband for the ionization electron energy. Therewith the impurity breakdown at the electric field perpendicular to this axis correlates with a classical picture.

Studying edge luminescence of n-3C-SiC epilayers grown on 6H-SiC substrates

Epitaxial films of cubic silicon carbide (n-3C-SiC) polytype grown on hexagonal (6H-SiC) polytype substrates by sublimation epitaxy in vacuum have been studied. The films of the best structural quality exhibit low-temperature photoluminescence related to the recombination of bound excitons. The results are compared to the available data for volume 3C-SiC crystals.