Photoelectric properties of porous GaN/SiC heterostructures

The origin of photoconductivity in porous structures formed by anodization of GaN/SiC heterostructures has been studied. It is shown by comparing the photoelectric, optical, electrical, and structural properties of untreated and anodized heterostructures that this effect is due to the presence of charged states at the interface between GaN and SiC that are specific to the anodization conditions.     

Formation of graphite/sic structures by the thermal decomposition of silicon carbide

The conditions in which carbon layers are synthesized on the surface of silicon carbide (SiC) wafers by thermal decomposition are studied. The effect of temperature and composition of the gas atmosphere on the structural properties of the layers being synthesized is analyzed. The conditions in which continuous graphite films with both single-crystal and polycrystalline structure can be obtained are determined.     

Transport properties of graphene films grown by thermodestruction of SiC (0001) surface in argon medium

We present the results of investigations of the transport properties of graphene films obtained by thermodestruction of a 4H-SiC (0001) surface in argon. The charge-carrier concentration in the graphene layer was within 7 × 10¹¹–1 × 10¹² cm^–2, and the maximum mobility of electrons approached 6000 cm²/(V · s). The achieved parameters of mobility are close to theoretical values calculated for graphene films with intrinsic conductivity on the Si face of SiC at Т = 300 К in the absence of intercalated hydrogen.

     

Optimization of Raw Material Mixes in Studying Mixed Cements and Their Physicomechnical Properties

Refractories and Industrial Ceramics - Results are provided for a study of the optimization of a three-component raw material mix for the production of mixed cement. Optimization was performed...     

New approach to rapid characterization of single-crystalline silicon carbide

A new approach to the characterization of single-crystalline silicon carbide (SiC) ingots is proposed, which can be used for the rapid diagnostics of material quality under large-scale commercial production conditions. The proposed method can reveal various defects, such as polytype inclusions, small-angle grain boundaries, dislocations, micropipes, and inhomogeneous dopant distribution and can be used to optimize technological regimes for growing bulk SiC single crystals.     

Optical and structural properties of SiC nanocrystals

This paper presents the results of porous SiC characterizations using photoluminescence, scanning electronic microscopy and X-ray diffraction techniques. It is shown that the intensity of defect-related PL bands (2.13 and 2.54 eV) increases monotonically with PSiC thickness rise from 2.0 up to 12.0 μm. These luminescence centers are assigned to surface defects which appear at the PSiC etching process. Intensity enhancement for exciton-related PL bands (2.84, 3.04 and 3.24 eV ) is attributed to the exciton recombination rate increasing as result of electron-hole confinement realization in big size SiC NCs (6H-PSiC with inclusions of 15R- and 4H-PSiC) and/or quantum confinement exciton recombination in small-size 4H-PSiC NCs.     

Low-temperature transport properties of multigraphene films grown on the SiC surface by sublimation

Multigraphene films grown by sublimation on the surface of a semi-insulating 6H-SiC substrate have been studied. It is shown that pregrowth annealing of the substrate in a quasiclosed growth cell improves the structural quality of a multigraphene film. Ohmic contacts to the film have been fabricated, and the Hall effect has been studied at low temperatures. It is found that a 2D electron gas exists in the films. It is concluded that the conductivity of the film is determined by defects existing within the graphene layer or at the interface between the graphene film and a SiC substrate.     

Magnesium outdiffusion from porous silicon carbide substrates during autodoping of gallium nitride epilayers

We have studied the outdiffusion of magnesium from silicon carbide substrates during autodoping of gallium nitride epilayers. The autodoping effect was observed in the case of porous substrates obtained by surface anodization of 6H-SiC wafers. It is established that the magnesium distribution profiles can be controlled by post-growth annealing. The fact of doping is confirmed by the results of photoluminescence measurements at 77 K.     

Collective effects in the system of structural defects in homoepitaxial GaN grown on porous substrates

Results of experiments on the homoepitaxial growth of gallium nitride (GaN) on porous GaN substrates with nanostructured volume are reported. A mechanism that can be used to exclude the dislocations of substrate from the sources of threading dislocations in homoepitaxial layers is described for the first time.     

Electrical characteristics of multigraphene films grown on high-resistivity silicon carbide substrates

Multigraphene films grown by sublimation of the surface of semi-insulating 6H-SiC substrates in a vacuum have been studied. The films exhibit a semiconductor-type conductivity. A conclusion is made that this type of conduction is supposedly determined by defects present between separate graphene crystals constituting the carbon layers under study.