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Saint Petersburg, United States

Strelchuk V.V.,Ukrainian Academy of Sciences | Kladko V.P.,Ukrainian Academy of Sciences | Avramenko E.A.,Ukrainian Academy of Sciences | Kolomys O.F.,Ukrainian Academy of Sciences | And 6 more authors.
Semiconductors | Year: 2010

High-resolution X-ray diffraction analysis and scanning confocal Raman spectroscopy are used to study the spatial distribution of strains in the InxGa1-xN/GaN layers and structural quality of these layers in a multilayered light-emitting diode structure produced by metal-organic chemical vapor deposition onto (0001)-oriented sapphire substrates. It is shown that elastic strains almost completely relax at the heterointerface between the thick GaN buffer layer and InxGa1-xN/GaN buffer superlattice. It is established that the GaN layers in the superlattice are in a stretched state, whereas the alloy layers are in a compressed state. In magnitude, the stretching strains in the GaN layers are lower than the compressive strains in the InGaN layers. It is shown that, as compared to the buffer layers, the layers of the superlattice contain a smaller number of dislocations and the distribution of dislocations is more randomly disordered. In micro-Raman studies on scanning through the thickness of the multilayered structure, direct evidence is obtained for the asymmetric gradient distributions of strains and crystal imperfections of the epitaxial nitride layers along the direction of growth. It is shown that the emission intensity of the InxGa1-xN quantum well is considerably (more than 30 times) higher than the emission intensity of the GaN barrier layers, suggesting the high efficiency of trapping of charge carriers by the quantum well. © 2010 Pleiades Publishing, Ltd. Source


Kladko V.P.,Ukrainian Academy of Sciences | Kuchuk A.V.,Ukrainian Academy of Sciences | Safriuk N.V.,Ukrainian Academy of Sciences | Machulin V.F.,Ukrainian Academy of Sciences | And 5 more authors.
Semiconductors | Year: 2011

The methods of high-resolution X-ray diffraction have been used to study the multilayered structures in an InxGa1 - xN/GaN system grown by the method of metal-organic chemical-vapor deposition. A correlation between the strain state (relaxation) of the system, the indium content within quantum wells, the ratio of the barrier/well thicknesses, and the number of quantum wells in the active superlattice is established. It is shown that partial relaxation is observed even in a structure with one quantum well. The results we obtained indicate that the relaxation processes are bound to appreciably affect the optical characteristics of devices. © 2011 Pleiades Publishing, Ltd. Source


Tsvetkova M.N.,Saint Petersburg State University | Korsakov V.G.,Saint Petersburg State University | Sychev M.M.,Saint Petersburg State University | Chernovets B.V.,Saint Petersburg State Polytechnic University | Itkinson G.V.,ZAO Svetlana Optoelectronics
Journal of Optical Technology (A Translation of Opticheskii Zhurnal) | Year: 2011

A comparative study has been carried out of the composition and the reflection and luminescence spectra of yttrium aluminum garnet and sialons as promising photophosphors. It is shown that the phase composition and surface inhomogeneity of the sialon particles has no effect on the position of the dopant levels in the band gap of the matrix or the photoluminescence spectra. It is established that the quantum efficiency of photophosphors synthesized on a sialon base and doped with europium is comparable with that of the garnet phosphor Y3Al5O12:Ce, and this makes it possible to use them in producing LEDs with white luminescence. The strength of the crystalline structure of sialons is significantly higher, and therefore the brightness and luminescence color of the photophosphors shows little dependence on time and temperature. © 2011 Optical Society of America. Source


Aladov A.V.,Russian Academy of Sciences | Vasilieva E.D.,ZAO Svetlana Optoelectronics | Zakgeim A.L.,Russian Academy of Sciences | Itkinson G.V.,ZAO Svetlana Optoelectronics | And 4 more authors.
Light and Engineering | Year: 2010

The article briefly discusses the history of the development of LEDs in Russia and abroad, the physical principles of their operation, and modern design, and manufacturing technology of high-wattage and energy efficient LEDs. Although it is devoted to the lighting systems based on LEDs, in particular, powerful color-dynamic RGB light source for biomedical purposes, as well as the prospects for further development of LEDs and some of unresolved problems. Source


Bogdanov A.A.,ZAO Svetlana Optoelectronics | Mokhnatkin A.E.,ZAO Svetlana Optoelectronics
Light and Engineering | Year: 2011

This paper contains a brief description of "Svetlana- Optoelectronics" company's current achievements and some prospects in the fi eld of manufacturing and application of powerful white light emitting diodes (LEDs) and LED-based lighting equipment (lamps). Source

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