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Engel’-Yurt, Russia

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.

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.

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.

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.

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.

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