On the origin of the redshift in the emission wavelength of InGaN/GaN blue light emitting diodes grown with a higher temperature interlayer

Cataloged from PDF version of article.A redshift of the peak emission wavelength was observed in the blue light emitting diodes of InGaN/GaN grown with a higher temperature interlayer that was sandwiched between the low-temperature buffer layer and high-temperature unintentionally doped GaN layer. The effect of interlayer growth temperature on the emission wavelength was probed and studied by optical, structural, and electrical properties. Numerical studies on the effect of indium composition and quantum confinement Stark effect were also carried out to verify the experimental data. The results suggest that the redshift of the peak emission wavelength is originated from the enhanced indium incorporation, which results from the reduced strain during the growth of quantum wells. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3694054

Исследование удельной электропроводности короткозамкнутой обмотки ротора асинхронных двигателей статистическим методом планирования эксперимента

Рассматривается влияние температуры и химсостава алюминия при заливке, длины пакетов и суммарного поперечного сечения пазов роторов на удельную электропроводность алюминия короткозамкнутой обмотки роторов асинхронных двигателей. В качестве метода исследования выбран экспериментально-статистический. Составлен центральный композиционный ротатабельный униформплан второго порядка. Для реализации плана изготовлено 116 экспериментальных роторов на базе двигателей серий АО и АО2. Удельная электропроводность измерялась прибором типа ИЭ-1 на вентиляционных крыльях, короткозамыкающих кольцах и на извлеченных из роторов стержнях обмотки. Всего произведено 4292 замера. В результате статистической обработки экспериментальных данных получены уравнения регрессии в виде полиномов второго порядка отдельно для короткозамыкающих колец и стержней обмотки. Проведена проверка уравнений на адекватность по F-критерию Фишера и коэффициентов уравнений на значимость по критерию Стъюдента. Уравнения регрессии позволяют учесть технологические и конструктивно-технологические факторы при проектировании асинхронных двигателей, аналогичных исследованным, и повысить точность расчета их характеристик

Investigation of AlGaN buffer layers on sapphire grown by MOVPE

In this work, AlGaN layers were grown on sapphire by metal-organic vapor phase epitaxy (MOVPE) on (0001)-oriented sapphire substrates, with the intention to investigate the effect of varying Al/MO and V/III ratios on the Al incorporation into the AlGaN layers. The parameters Al/MO and V/III describe the proportions of source material inside the reactor. With the help of optical transmission measurements, characteristic cut-off wavelengths of the Al xGa(1-x)N layers were determined. These wavelengths were used to calculate the Al content x of the layers, leading to values between 26.6% and 52.1%. Using the two process parameters Al/MO and V/III as input and the Al content of the AlGaN layers as a response variable, the experimental results were further investigated with the help of the software STATGRAPHICS. An estimated response surface for the variable x was generated. It was found that the Al incorporation is only tunable within a wide range for high V/III ratios of about 900. For constant Al/MO ratios and varying V/III ratios, two different growth characteristics were observed at high and low Al/MO values. This behavior is ascribed to the superposition of two oppositional effects

InGaN/GaN based LEDs with electroluminescence in violet, blue, and green tuned by epitaxial growth temperature

[No abstract available

Совершенствование технологии сооружения подводных переходов трубопроводов проложенных методом горизонтально-направленного бурения

Цель работы – разработка рекомендаций по применению технологии прокладки трубопроводов методом горизонтально-направленного бурения с применением защитного устройства. В процессе исследования проводились сравнительная характеристика существующих методов бестраншейной прокладки трубопроводов, расчет основных характеристик подводного перехода, подбор защитного устройства, исследование напряженно-деформированного состояния трубопровода с помощью конечно-элементного моделирования в программном комплексе Ansys. В результате исследования подобраны оптимальные параметры подводного перехода, методом конечно-элементного моделирования в программном комплексе Ansys определено напряженно-деформированнон состояние трубопровода с защитным устройством и без него.The purpose of the work is to develop recommendations for the application of pipeline laying technology by the method of horizontal directional drilling using a protective device. In the process of the research, the existing methods of trenchless pipeline laying, the calculation of the main characteristics of the underwater crossing, the selection of the protective device, the study of the stress-strain state of the pipeline using finite element modeling in the software complex Ansys were compared. As a result of the research, optimal parameters of the underwater transition were selected, the finite element method in the software complex Ansys determined the stress-strain state of the pipeline with the protective device and without it

On the Effect of Step-Doped Quantum Barriers in InGaN/GaN Light Emitting Diodes

Cataloged from PDF version of article.InGaN/GaN light-emitting diodes (LEDs) make an important class of optoelectronic devices, increasingly used in lighting and displays. Conventional InGaN/GaN LEDs of c-orientation exhibit strong internal polarization fields and suffer from significantly reduced radiative recombination rates. A reduced polarization within the device can improve the optical matrix element, thereby enhancing the optical output power and efficiency. Here, we have demonstrated computationally that the step-doping in the quantum barriers is effective in reducing the polarization-induced fields and lowering the energy barrier for hole transport. Also, we have proven experimentally that such InGaN/GaN LEDs with Si step-doped quantum barriers indeed outperform LEDs with wholly Si-doped barriers and those without doped barriers in terms of output power and external quantum efficiency. The consistency of our numerical simulation and experimental results indicate the effects of Si step-doping in suppressing quantum-confined stark effect and enhancing the hole injection, and is promising in improving the InGaN/GaN LED performance

Western Star, 1915-03-31

The Western Star began publication on Newfoundland's west coast on 4 April 1900, appearing weekly with brief semiweekly periods up to 1952, when it became a daily. As of 17 April 2019 it continues as a free weekly community paper

Influence of RuOx Gate Thermal Annealing on Electrical Characteristics of AlxGa1-xN/GaN HEMTs on 200-mm Silicon

10.1149/2.008402sslECS Solid State Letters32Q5-Q