Fully porous GaN p-n junction diodes fabricated by chemical vapor deposition

Producción CientíficaModern society is experiencing an ever-increasing demand for energy to power a vast array of electrical and mechanical devices. A significant amount of the energy consumed is used for lighting purposes. For instance, this demand is ~17% of the total energy consumed in the USA in 2011 [1]. Thus, any approach that can reduce energy consumption is important. In this context, the development of light emitting diodes (LEDs) incorporating at least one porous component, with improved light extraction efficiency, is being explored intensively [2]. However, up to now, only partially porous p-n junctions have been analyzed for this purpose.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA166A11-2 and VA293U1

Fabrication of p-type porous GaN on silicon and epitaxial GaN

Abstract : Porous GaN layers are grown on silicon from gold or platinum catalyst seed layers, and self-catalyzed on epitaxial GaN films on sapphire. Using a Mg-based precursor, we demonstrate p-type doping of the porous GaN. Electrical measurements for p-type GaN on Si show Ohmic and Schottky behavior from gold and platinum seeded GaN, respectively. Ohmicity is attributed to the formation of a Ga2Au intermetallic. Porous p-type GaN was also achieved on epitaxial n-GaN on sapphire, and transport measurements confirm a p-n junction commensurate with a doping density of 1018 cm 3. Photoluminescence and cathodoluminescence confirm emission from Mg-acceptors in porous p-type GaN

Fully porous GaN p-n junctions fabricated by Chemical Vapor Deposition: a green technology towards more efficient LEDs

Producción CientíficaPorous GaN based LEDs produced by corrosion etching techniques demonstrated enhanced light extraction efficiency in the past. However, these fabrication techniques require further postgrown processing steps, which increase the price of the final system. In this paper, we review the process followed towards the fabrication of fully porous GaN p-n junctions directly during the growth step, using a sequential chemical vapor deposition (CVD) process to produce the different layers that form the p-n junction.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA302U13

Обеспечение надежности головных подшипников судовых малооборотных двигателей, работающих на режимах частичных нагрузок

 The paper analyzes the causes of damage to the head bearings of low-speed marine engines of MAN B & W, mainly operating under partial load conditions. It has been established that diesel engines bearings with installed TCCO systems (Turbocharger Cut-Out) are the most damaging. TCCO systems allow gas turbochargers (TC) to be withdrawn from service in order to increase the productivity of the remaining turbochargers and reduce the specific fuel consumption. The results of a dynamic analysis of loading conditions for a bearing assembly are presented using the example of the 12K98MC engine for 100% and 50% Nen modes. It is established that the maximum force acting on the crosshead is 7755 kN and arises at the position of the crankshaft at an angle j = 205 ° and the angle of deflection of the connecting rod β = 8 °. In the operating mode of the engine 12K98MC-C6 100% Nen, no forces occurs in the crank mechanism, which help unload the lower bearing of the head bearing. The authors refute the assumption that there are damages to the antifriction layer of fatigue bearing. It is assumed that the main cause of such damage is the violation of the hydrodynamic lubrication regime with a decrease in the engine speed of the crankshaft. It is indicated the need to change the design of the lower bearing shell of the head bearing in order to increase the bearing capacity. A simplified 3D model of connecting rod and crosshead bearing was developed without a central oil distribution groove. The results of numerical modeling of the contact conditions of the upgraded version of the lower bearing of the head bearing are presented and the character of stress distribution and deformation in the volumes of the AlSn40 antifriction material is studied. It is established that the maximum pres­sure zones are located in the central part of the liner and in its peripheral areas. The obtained results of the investigation of the stressed-deformed state of the lower liner indicate the need to eliminate the axial oil distribution groove and the manufacture of axial oil distribution grooves under a total angle of 68 ... 72 °. The proposed version of the lower liner design at the engine operating mode of 100% Nen senses the maximum stresses and relative deformations in the bearing antifriction material 28 MPa and 22,5 ½ 10-3 respectively.   В работе приведён анализ причин повреждения головных подшипников малооборотных судовых двигателей фирмы MAN B&W, преимущественно работающих на режимах частичных нагрузок. Представлены результаты динамического анализа условий нагружения подшипникового узла на примере двигателя 12K98MC. Авторами опровергается предположение наличия повреждений антифрикционного слоя подшипников усталостного характера. Приведены результаты численного моделирования условий контакта модернизированного варианта нижнего вкладыша головного подшипника. Представлены результаты исследования напряжённо-деформированного состояния нижнего вкладыша и рекомендации по оптимизации его конструкции.

The Influence of Technological Parameters of X70 Stainless Steel Ladle Refining on the Residual Content of Non-Metallic Inclusions

It is demonstrated that during secondary refining at the ladle furnace the carbon content of steel and the residence time of the metal in the ladle exert a significant impact on the residual content of non-metallic inclusions (NMI) in steel. Mathematical calculations showed that the dynamic forces have minor effect on the motion of small sized NMI, making it difficult to penetrate deep into the slag

The Influence of Technological Parameters of X70 Stainless Steel Ladle Refining on the Residual Content of Non-Metallic Inclusions

It is demonstrated that during secondary refining at the ladle furnace the carbon content of steel and the residence time of the metal in the ladle exert a significant impact on the residual content of non-metallic inclusions (NMI) in steel. Mathematical calculations showed that the dynamic forces have minor effect on the motion of small sized NMI, making it difficult to penetrate deep into the slag

Reduced workfunction intermetallic seed layers allow growth of porous n-GaN and low resistivity, ohmic electron transport

Porous GaN crystals have been successfully grown and electrically contacted simultaneously on Pt- and Au-coated silicon substrates as porous crystals and as porous layers. By the direct reaction of metallic Ga and NH3 gas through chemical vapor deposition, intermetallic metal-Ga alloys form at the GaN–metal interface, allowing vapor–solid–solid seeding and subsequent growth of porous GaN. Current–voltage and capacitance–voltage measurements confirm that the intermetallic seed layers prevent interface oxidation and give a high-quality reduced workfunction contact that allows exceptionally low contact resistivities. Additionally, the simultaneous formation of a lower workfunction intermetallic permits ohmic electron transport to n-type GaN grown using high workfunction metals that best catalyze the formation of porous GaN layers and may be employed to seed and ohmically contact a range of III-N compounds and alloys for broadband absorption and emission

The downregulation of the Miniature gene does not replicate Miniature loss-of-function phenotypes in Drosophila melanogaster wing to the full extent

During maturation Drosophila wing epithelial cells undergo number of changes due to processes, which take place in the wing of the newly emerged fly, among which epithelial-to-mesenchymal transition (EMT) and apoptosis are pivotal. It is considered that neurohormone bursicon is responsible for their triggering. In turn, extracellular matrix protein Miniature is also essential for proper progress of apoptosis and, presumably, EMT. In accordance with our previously proposed hypothesis, Miniature and bursicon form stabilizing/accumulative complexes, which are able to diffuse freely within Drosophila wing, in such a way constitutively promoting enough concentrations of the maturation triggering signal. Here we tried to come to confirmation of our hypothesis from the other side, using UAS/GAL4 system and RNAi-silencing techniques

Mantis Religiosa (Dyctioptera, Mantidae) Infected by Wolbachia

For the first time, endosymbiotic bacteria of the genus Wolbachia were found to infect soothsayers, Mantis religiosa (Linnaeus, 1758). Mantises were collected at two locations in vicinity of Mykolaiv and Kaniv, Ukraine. Tested individuals were not infected by Cardinium and Spiroplasma.Впервые установлено наличие эндосимбиотических бактерий рода Wolbachia у богомолов Mantis religiosa (Linnaeus, 1758). Богомолы были пойманы в двух местонахождениях (окрестности Николаева и Канева, Украина). Особи не были инфицированы бактериями родов Cardinium и Spiroplasma

Metal catalyzed porous n-type GaN layers: low resistivity ohmic contacting and single-step MgO/GaN diode formation

Porous GaN crystals have been successfully grown and electrically contacted simultaneously on Pt- and Au-coated silicon substrates as porous crystals and as porous layers. By the direct reaction of metallic Ga and NH3 gas through chemical vapor deposition, intermetallic metal-Ga alloys form at the GaN-metal interface, allowing vapoursolid- solid seeding and subsequent growth of porous GaN. Currentvoltage and capacitance-voltage measurements confirm that the intermetallic seed layers prevent interface oxidation and give a highquality reduced workfunction contact that allows exceptionally low contact resistivity. Additionally, the simultaneous formation of a lower workfunction intermetallic permits ohmic electron transport to n-type GaN grown using high workfunction metals that best catalyze the formation of porous GaN layers and may be employed to seed and ohmically contact a range of III-N compounds and alloys for broadband absorption and emission. Additionally, we show how a porous GaN rectifying diode can be formed by oxidatively crystallizing Mg typically employed for p-doping GaN, as a layer formed under porous structure resulting in a high-k polycrystalline MgO dielectric