Deer Park, NY, United States
Deer Park, NY, United States

Time filter

Source Type

Reshchikov M.A.,Virginia Commonwealth University | McNamara J.D.,Virginia Commonwealth University | Usikov A.,Nitride Crystals Inc. | Usikov A.,Saint Petersburg National Research University of Information Technologies | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

An unusual temperature dependence of the photoluminescence lifetime for the green luminescence (GL) band in GaN is explained. This GL is caused by an internal transition of electrons from an excited state to the ground state of the 0/+ transition level of the isolated CN defect. The excited state appears only after the CN defect captures two photogenerated holes. The electron capture by the excited state is nonradiative, yet the lifetime of such can be probed by the temperature variation of the GL lifetime, whose temperature dependence shows a classic case of electron capture by a giant trap. © 2016 American Physical Society.


Reshchikov M.A.,Virginia Commonwealth University | Usikov A.,Nitride Crystals Inc. | Usikov A.,Saint Petersburg National Research University of Information Technologies | Helava H.,Nitride Crystals Inc. | Makarov Y.,Nitride Crystals Inc.
Applied Physics Letters | Year: 2014

Many point defects in GaN responsible for broad photoluminescence (PL) bands remain unidentified. Their presence in thick GaN layers grown by hydride vapor phase epitaxy (HVPE) detrimentally affects the material quality and may hinder the use of GaN in high-power electronic devices. One of the main PL bands in HVPE-grown GaN is the red luminescence (RL) band with a maximum at 1.8 eV. We observed the fine structure of this band with a zero-phonon line (ZPL) at 2.36 eV, which may help to identify the related defect. The shift of the ZPL with excitation intensity and the temperature-related transformation of the RL band fine structure indicate that the RL band is caused by transitions from a shallow donor (at low temperature) or from the conduction band (above 50 K) to an unknown deep acceptor having an energy level 1.130 eV above the valence band. © 2014 AIP Publishing LLC.


Makarov Y.,Nitride Crystals Inc. | Makarov Y.,Nitride Crystals Ltd | Litvin D.,Nitride Crystals Ltd | Vasiliev A.,Nitride Crystals Ltd | Nagalyuk S.,Nitride Crystals Ltd
Materials Science Forum | Year: 2016

Recently, the wide bandgap semiconductors, especially silicon carbide (SiC), have become more important due to the unique electrical and thermophysical properties that make them applicable to a variety of electronic devices (Schottky and PiN diodes, JFETs, MOSFETs, etc.). For these applications, the crystals need to be manufactured with highest possible quality, both structural and chemical, at reduced cost. This requirement places rather extreme constraints on the crystal growth as the simultaneous goals of high quality and low cost are generally incompatible. Refractory metal carbide technology, particularly, tantalum carbide (TaC), was originally developed for application in highly corrosive and reactive environments. Yu. Vodakov [1] demonstrated for the first time advantages of use of refractory metal carbides for PVT growth of SiC and later AlN bulk crystals. In the present paper we discuss the effect of refractory metal on PVT growth of large diameter 4H SiC bulk crystals. © 2016 Trans Tech Publications, Switzerland.


Polyakov A.Y.,Chonbuk National University | Smirnov N.B.,National University of Science and Technology "MISIS" | Yakimov E.B.,Russian Academy of Sciences | Usikov A.S.,Nitride Crystals Inc. | And 6 more authors.
Journal of Alloys and Compounds | Year: 2014

Two sets of undoped GaN films with the thickness of 10-20 μm were prepared by hydride vapor phase epitaxy (HVPE) and characterized by capacitance-voltage (C-V) profiling, microcathodoluminescence (MCL) spectra measurements, MCL imaging, electron beam induced current (EBIC) imaging, EBIC dependence on accelerating voltage, deep levels transient spectroscopy, high resolution X-ray diffraction measurements. The difference in growth conditions was mainly related to the lower (850 °C, group 1) or higher (950 °C, group 2) growth temperature. Both groups of samples showed similar crystalline quality with the dislocation density close to 108 cm-2, but very different electrical and optical properties. In group 1 samples the residual donors concentration was ∼1017 cm-3 or higher, the MCL spectra were dominated by the band-edge luminescence, and the diffusion length of charge carriers was close to 0.1 μm. Group 2 samples had a 2-4.5 μm thick highly resistive layer on top, for which MCL spectra were determined by green, yellow and red defect bands, and the diffusion length was 1.5 times higher than in group 1. We also present brief results of growth at the "standard" HVPE growth temperature of 1050 °C that show the presence of a minimum in the net donor concentration and deep traps density as a function of the growth temperature. Possible reasons for the observed results are discussed in terms of the electrical compensation of residual donors by deep traps. © 2014 Elsevier B.V. All rights reserved.


Reshchikov M.A.,Virginia Commonwealth University | Demchenko D.O.,Virginia Commonwealth University | Usikov A.,Nitride Crystals Inc. | Usikov A.,Saint Petersburg National Research University of Information Technologies | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

In high-purity GaN grown by hydride vapor phase epitaxy, the commonly observed yellow luminescence (YL) band gives way to a green luminescence (GL) band at high excitation intensity. We propose that the GL band with a maximum at 2.4 eV is caused by transitions of electrons from the conduction band to the 0/+ level of the isolated CN defect. The YL band, related to transitions via the -/0 level of the same defect, has a maximum at 2.1 eV and can be observed only for some high-purity samples. However, in less pure GaN samples, where no GL band is observed, another YL band with a maximum at 2.2 eV dominates the photoluminescence spectrum. The latter is attributed to the CNON complex.


Solomonov A.V.,St Petersburg Electrotechnical University Leti | Tarasov S.A.,St Petersburg Electrotechnical University Leti | Men'kovich E.A.,St Petersburg Electrotechnical University Leti | Lamkin I.A.,St Petersburg Electrotechnical University Leti | And 6 more authors.
Semiconductors | Year: 2014

The results of work on developing and studying ultraviolet (UV) light-emitting diodes (LEDs) based on GaN/AlGaN heterostructures fabricated on Al2O3(0001) substrates by the chloride-hydride vaporphase epitaxy are presented. The maximum in the electroluminescence spectrum is located in the wavelength range of 360-365 nm, and its full width at half maximum is 10-13 nm. At a working current of 20 mA, the optical density and efficiency of the UV LED are 1.14 mW and 1.46%, respectively. © 2014 Pleiades Publishing, Ltd.


Kurin S.,Nitride Crystals Ltd. | Antipov A.,Nitride Crystals Ltd. | Barash I.,Nitride Crystals Ltd. | Roenkov A.,Nitride Crystals Ltd. | And 5 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2013

In this paper, we present results on development of ultraviolet light-emitting diodes (UV LEDs) based on GaN/AlGaN heterostructures grown on Al2O3 (0001) substrates by chloride-hydride vapour phase epitaxy (CHVPE). Both packaged and unpackaged UV LED dies were fabricated. The peak wavelengths of dies were in the range of 360-365 nm with a typical FWHM of 10-13 nm. UV LEDs proved performance capability at current density up to 125 A/cm2. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Menkovich E.A.,Saint Petersburg Electrotechnical University | Tarasov S.A.,Saint Petersburg Electrotechnical University | Lamkin I.A.,Saint Petersburg Electrotechnical University | Kurin S.Yu.,GaN Crystals Ltd. | And 5 more authors.
Journal of Physics: Conference Series | Year: 2013

In this paper we report on dependence of the temperature of active layers (ALs) of heterostructures of light-emitting diodes (LEDs) based on AlGaN (UV LEDs) and InGaN (blue LEDs) on various current values (up to 150 mA). It is shown that the heating of the heterostructures is directly related to the concentration of defects. UV LEDs are characterized by a higher temperature than blue LEDs, they also demonstrate a lower wall-plug efficiency (WPE) (about 1.5% at 20 mA). The WPE of blue LEDs with and without the superlattice are 15% and 18%, respectively. To verify the accuracy of the performed measurements the theoretical calculation of the AL temperature according to Van Roosbroeck-Shockley theory and the model of 2D-combined density of states is carried out. © Published under licence by IOP Publishing Ltd.


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.


PubMed | Virginia Commonwealth University and Nitride Crystals Inc.
Type: | Journal: Scientific reports | Year: 2016

Point defects in high-purity GaN layers grown by hydride vapor phase epitaxy are studied by steady-state and time-resolved photoluminescence (PL). The electron-capture coefficients for defects responsible for the dominant defect-related PL bands in this material are found. The capture coefficients for all the defects, except for the green luminescence (GL1) band, are independent of temperature. The electron-capture coefficient for the GL1 band significantly changes with temperature because the GL1 band is caused by an internal transition in the related defect, involving an excited state acting as a giant trap for electrons. By using the determined electron-capture coefficients, the concentration of free electrons can be found at different temperatures by a contactless method. A new classification system is suggested for defect-related PL bands in undoped GaN.

Loading Nitride Crystals Inc. collaborators
Loading Nitride Crystals Inc. collaborators