In this paper, we report on growth of ultraviolet light-emitting diode (UV LED) heterostructures by hydride vapour phase epitaxy (HVPE) on sapphire substrates and results of the heterostructures characterization by X-ray diffractometry, scanning electron microscopy, photo- and electroluminescence, micro-photoluminescence, collected from the cleaved edges and the surface of the heterostructure with lateral resolution of about 1 mu m. The heterostructures demonstrate efficient hole injection and low droop of the external quantum efficiency. Packaged 360 nm UV LED chips have wall-plug efficiency of 1-1.5 %. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The effect of superlattice adding on the luminescence properties of heterostructures based on (Al,In,Ga)N was investigated. It is shown that using structures with two superlattices: the InGaN/InGaN under active region and the AlGaN/GaN as a top p-layer gives the best effect. The elastic stresses on heterointerface of these structure are compensated optimally. As a result they are the most effective and stable functionality.

We report on results of the performance study of UVA LEDs depending on the thickness of the active region. UVA LEDs are based on GaN/AlGaN heterostructures grown on Al2O3 (0001) substrates by hydride vapor phase epitaxy (HVPE). It is shown that the use of thick (-100 nm) single layer as the active region of UVA LED is a promising concept to achieve enhanced efficiency.

The paper is devoted to the development and study of solar-blind and visible-blind photodetectors. We report on the spectral characteristics of the ultraviolet photodetectors based on Shottky barrier to the epitaxial layers of the n-AlxGa1-xN solid solutions. The use of Schottky barrier photodiodes is advantageous since it does not require the growth of additional epitaxial layer of p-type conductivity.

The results of an investigation into the properties of double-layer metal contacts to the epitaxial layers of AlxGa1-xN solid solutions for ultraviolet photodetectors and UHF electronic devices are presented. The processes of atom redistribution during the formation of metal layers and their subsequent annealing to form low resistance contacts were studied by Auger electron spectroscopy. The results obtained allowed us to develop a technique for creating ohmic contacts having low resistance value.

The effect of addition of superlattice (SL) and the structure of the upper barrier layer on the luminescence processes occurring in light-emitting nanoheterostructures was studied. It was shown that the optimum is using of structures with two SL: InGaN / InGaN structure in the lower part and the AlGaN / GaN for the top p-layer. It is shown that the using of the SL InGaN / InGaN in the vicinity of the active region optimally compensate the elastic stresses and the piezoelectric field at the hetero boundaries. Such compensation of elastic stresses reduces the formation of dislocations in these structures, which increases the radiation intensity.

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/cm(2). (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Light emitting nanostructures on the basis of (Al, Ga, In) N solid solutions with and without superlattices were investigated. Experiments in a wide range of temperatures (10-300 K) and currents (10 nA - 2 mA) were done. Comparison of structures with and without superlattices was performed. It was found that the structure with superlattices has higher stability and better work performance. Apparently, the use of superlattices can reduce an influence of elastic stresses and piezoelectric fields at the heterointerface. This may decrease the formation of dislocations, which increases the intensity of radiation and decreases self-heating effects.

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 m.). 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.

In this paper we report on results of 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 UV LED heterostructures and packaged dies are investigated. UV LEDs proved performance capability at current density up to 125 A/cm(2) and revealed wall-plug efficiency (WPE) of 1.5% at operating current of 20 mA.

Light-emitting diode structures on the basis of (Al, Ga, In)N solid solutions with and without superlattices were investigated. Experiments in a wide range of temperatures (10-300 K) and noise currents (10 nA - 2 mA) were performed. It was found that the structure with superlattices has a higher stability and better work performance. Apparently, the use of superlattices can compensate for the elastic stresses and piezoelectric fields at the heterointerface. This compensation reduces the formation of dislocations in the structures with superlattices, which increases the intensity of radiation and decreases self-heating effects.