Nitride Crystals Group Ltd.

Engel’-Yurt, Russia

Nitride Crystals Group Ltd.

Engel’-Yurt, Russia
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Usikov A.,Nitride Crystals Inc. | Usikov A.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Nikiforov A.,Boston University | Khait O.,Multitech Ltd. | And 11 more authors.
Materials Science Forum | Year: 2017

GaN, GaN/AlGaN and GaN/InGaN-based structures were used to study water photoelectrolysis in KOH-based electrolyte, measurement of current-potential characteristics, investigation of electrode corrosion and for hydrogen generation. The corrosion process of p-n AlGaN/GaN structure starts in the p-layers, spreads via vertical channels associated with threading defects, and continues laterally along the n-layers, where large local hollows and voids were observed. The H2 production rate of 0.3-0.6 ml/cm2×h was measured for n-GaN structure. © 2017 Trans Tech Publications, Switzerland.


Usikov A.,Nitride Crystals Inc. | Usikov A.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Ermakov I.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Helava H.,Nitride Crystals Inc. | And 8 more authors.
Physica Status Solidi (B) Basic Research | Year: 2017

Specifics of the water photoelectrolysis in KOH-base aqueous solution using GaN-based structures as working electrodes are studied. The structures were grown by HVPE and MOCVD techniques on sapphire substrates. In highly Si-doped HVPE-grown GaN layers (ND−NA ∼ 3 × 1018 cm−3) a barrier at the E1 offset potential dominates the current–potential (I–E) characteristics. The same dominant E1 offset potential was observed in MOCVD-grown GaN/InGaN nanopillar structures after the treatment. The Debye screening effect in high-concentration of KOH electrolyte (20–40 wt.%) that reduces the potential barrier was observed clearly in the defectless nanopillar structures. The corrosion process is initiated in the top p-type layers via channels associated with threading defects and can penetrate deeply into the structure. It further proceeds in a lateral direction in n-type layers forming voids and cavities in the structure. The H2 production rate of 0.3–0.6 ml cm−2 h−1 was measured for n-GaN-based structure in KOH electrolyte under the Xe-lamp illumination (concentration factor ×15). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


Zubenko T.K.,Herzen University | Puzyk M.V.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Stozharov V.M.,Herzen University | Ermakov I.A.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | And 8 more authors.
Journal of Physics: Conference Series | Year: 2016

Etching of the GaN layers in 1M KOH aqua solution under irradiation was studied by the electro-stimulated photolysis using N2-laser (337 nm, 60 W/m2) as a light source. It was observed that the size and the depth of the failure monotonically depend on the optical power and the irradiation time of the N2 laser and the GaN layer type of conductivity. The GaN layers etching rate was evaluated. A mechanism of the failure in the n-GaN layers is discussed. © Published under licence by IOP Publishing Ltd.


Kurin S.Y.,Nitride Crystals Group Ltd. | Puzyk M.V.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Ermakov I.A.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Antipov A.A.,Nitride Crystals Group Ltd. | And 8 more authors.
Journal of Physics: Conference Series | Year: 2016

In this work we correlated transmission spectra of GaN layers grown on sapphire substrates by hydride vapour phase epitaxy with biaxial stress measured in the layers. It was observed that the sign of stress in the GaN layer is changed by Si doping and growth conditions. Transmission curves are shifted relative to each other depending on the stress in the layer. The cut-off wavelength of the transmission curves has a tendency to shift near parallel to a shorter wavelength range when the GaN layer is under the compression biaxial stress. When the GaN layer is under the tensile biaxial stress the cut off wavelength has a tendency to shift near parallel to a longer wavelength range). © Published under licence by IOP Publishing Ltd.


Fomichev A.D.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Kurin S.Y.,Nitride Crystals Group Ltd. | Ermakovi I.A.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Puzyk M.V.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | And 6 more authors.
Journal of Physics: Conference Series | Year: 2016

Direct water photoelectrolysis using III-N materials is a promising way for hydrogen production. GaN/AlGaN based p-n structures were used in a photoelectrochemical process to investigate the material etching (corrosion) in an electrolyte. At the beginning, the corrosion performs through the top p-type layers via channels associated with threading defects and can penetrate deep into the structure. Then, the corrosion process occurs in lateral direction in n- type layers forming voids and cavities in the structure. The lateral etching is due to net positive charges at the AlGaN/GaN interfaces arising because of spontaneous and piezoelectric polarization in the structure and positively charged ionized donors in the space charge region of the p-n junction. © Published under licence by IOP Publishing Ltd.


Usikov A.,Nitride Crystals Inc. | Usikov A.,Saint Petersburg State University of Information Technologies, Mechanics and Optics | Kurin S.,Nitride Crystals Group Ltd. | Barash I.,Nitride Crystals Group Ltd. | And 7 more authors.
Materials Science Forum | Year: 2016

Hydride Vapor Phase Epitaxy (HVPE) was used to grow 1-4 μm thick undoped GaN layers on 4H-SiC and sapphire substrates. To adjust mechanical strain and crack formation in the GaN/SiC samples, the AlGaN-based buffer layer was grown at low temperature (920-980ºC) and the GaN layer was grown at a higher temperature (1000-1040ºC). Laser scribing through the GaN layer or the SiC substrate was applied to fabricate dies from the GaN/SiC and GaN/sapphire samples. The laser irradiation passing through the GaN layer to the sapphire substrate or through the SiC substrate to the GaN layer, along two orthogonal directions created a net of micro-cavities in sapphire and melted grooves in SiC that promote easy breakage of the sample into rectangular dies. © 2016 Trans Tech Publications, Switzerland.


Medvedev O.S.,Saint Petersburg State University | Khait O.,Multitech Ltd. | Kurin S.Yu.,Nitride Crystals Group Ltd. | Usikov A.S.,Nitride Crystals Inc. | And 3 more authors.
Journal of Physics: Conference Series | Year: 2015

We report on intra-volume laser scribing process developed for GaN layers grown on single-side and double-side c-plane sapphire structures by hydride vapor phase epitaxy. Dies of 10 mm × 10 mm and 15 mm × 15 mm were cut from 2-inch wafers using a 1.064-μm Nd:YAG pulsed laser. The impact of laser cutting on the mechanical properties of GaN/Al2O3 structures is discussed.


Evseenkov A.S.,Saint Petersburg Electrotechnical University | Tarasov S.A.,Saint Petersburg Electrotechnical University | Kurin S.Yu.,Nitride Crystals Group Ltd. | Usikov A.S.,Nitride Crystals Inc. | And 4 more authors.
Journal of Physics: Conference Series | Year: 2015

The UV LED GaN/AlGaN heterostructures obtained by HVPE approach were investigated. It was shown that the peak wavelength of UV LEDs was in the range of 360-380 nm with FWHM of 10-13 nm. At operating current of 20 mA, the active region temperature Tj was 43°C, the output optical power and efficiency - 1.14 mW and 1.46%, respectively. It was shown that the use of HVPE method allowed to achieve a high degree of structural perfection of epitaxial structures. © Published under licence by IOP Publishing Ltd.


Puzyk M.V.,Herzen University | Usikov A.S.,Nitride Crystals Inc. | Kurin S.Yu.,Nitride Crystals Group Ltd. | Puzyk A.M.,Herzen University | And 7 more authors.
Journal of Physics: Conference Series | Year: 2015

GaN layers of n-type and p-type conductivity grown by HVPE on sapphire substrates were used as working electrodes for water electrolysis, photoelectrolysis and hydrogen gas generation. Specifically the water splitting process is discussed. Corrosion of the GaN materials is also considered. The hydrogen production rate under 365-nm UV LED irradiation of the GaN and external bias was 0.3 ml/(cm2∗h) for an n-GaN photoanode (n∼8×1016 cm-3) in 1M Na2SO4 electrolyte and 1.2 ml/(cm2∗h) for an n-GaN photoanode (n∼1×1017 cm-3) in 1M KOH electrolyte.


Reshchikov M.A.,Virginia Commonwealth University | Usikov A.,Nitride Crystals Inc. | Helava H.,Nitride Crystals Inc. | Makarov Y.,Nitride Crystals Inc. | And 3 more authors.
Journal of Electronic Materials | Year: 2016

Gallium nitride, grown by hydride vapor phase epitaxy and capped with a thin AlGaN layer, was studied by photoluminescence (PL) methods. The concentration of free electrons in GaN was found from the time-resolved PL data, and the concentrations of point defects were estimated from the steady-state PL measurements. The intensity of PL from GaN decreases moderately after capping it with Si-doped AlGaN, and it decreases dramatically after capping with Mg-doped AlGaN. At the same time, the concentration of free electrons and the concentrations of main radiative defects in GaN are not affected by the AlGaN capping. We demonstrate that PL is a powerful tool for nondestructive characterization of semiconductor layers buried under overlying device structures. © 2015, The Minerals, Metals & Materials Society.

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