light-emitting

Monolithic Broadband InGaN Light-Emitting Diode

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Monolithic Broadband InGaN Light-Emitting Diode by Cong Feng, Jian-An Huang, Hoi Wai Choi.

A monolithic nonphosphor broadband-emission light-emitting diode is demonstrated, comprising a combination of high-density microstructured and nanostructured InGaN-GaN quantum wells fabricated using top-down approach. Broadband emission achieved by taking advantage low-dimensional-induced strain-relaxation highly strained wells, combining light emitted from strain-relaxed nanotips at wavelengths shorter than the as-grown as much 80 nm with longer-wavelength larger nonrelaxed microdisks. The localized characteristics have been studied spatially resolved near-field photoluminescence spectroscopy which enabled both intensity spectrum individual to be distinguished larger-dimensioned regions. Distinctive blue-green-yellow can observed electroluminescent device, whose continuous broadband characterized CIE coordinates (0.39, 0.47) color rendering in…

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Carrier distribution in (0001)InGaN∕GaN multiple quantum well light-emitting diodes

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Carrier distribution in (0001)InGaN∕GaN multiple quantum well light-emitting diodes by Aurelien David, Michael Grundmann, John F. Kaeding, Nathan F. Gardner, Theodoros G. Mihopoulos, Michael R. Krames.

We study the carrier distribution in multi quantum well (multi-QW) InGaN light-emitting diodes. Conventional wisdom would assume that a large number of QWs lead to smaller density per QW, enabling efficient recombination at high currents. use angle-resolved far-field measurements determine location spontaneous emission series multi-QW samples. They reveal that, no matter how many are grown, only QW nearest p layer emits light under electrical pumping, which can limit performances high-power devices.

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Multiple-exposure colloidal lithography for enhancing light output of GaN-based light-emitting diodes by patterning Ni/Au electrodes

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Multiple-exposure colloidal lithography for enhancing light output of GaN-based light-emitting diodes by patterning Ni/Au electrodes by Zhuo Xiong, Tongbo Wei, Yonghui Zhang, Junxi Wang, Jinmin Li.

Ni/Au electrodes with single, twined and triplet hole array patterns light-emitting diodes have been fabricated by multiple-exposure colloidal lithography. It is found that 45.6%, 83.6% 15.5% improvement in light output at 350 mA has achieved patterning twined, arrays. In addition, patterned LEDs possess much larger view angles than non-patterned ones due to scattering effects of around the holes, especially for LEDs. Our proposed method fabricating multiple holes structure would be very promising improve power when using advanced electrodes.

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High light extraction efficiency in bulk-GaN based volumetric violet light-emitting diodes

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High light extraction efficiency in bulk-GaN based volumetric violet light-emitting diodes by Aurelien David, Christophe A. Hurni, Rafael I. Aldaz, Michael J. Cich, Bryan Ellis, Kevin Huang, Frank M. Steranka, Michael R. Krames.

We report on the light extraction efficiency of III-Nitride violet light-emitting diodes with a volumetric flip-chip architecture. introduce an accurate optical model to account for extraction. fabricate series devices varying configurations and fit their measured performance our model. show importance second-order effects like photon recycling residual surface roughness data. conclude that reach 89%.

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Multicolor Silicon Light-Emitting Diodes (SiLEDs)

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Multicolor Silicon Light-Emitting Diodes (SiLEDs) by Florian Maier-Flaig, Julia Rinck, Moritz Stephan, Tobias Bocksrocker, Michael Bruns, Christian Kübel, Annie K. Powell, Geoffrey A. Ozin, Uli Lemmer.

We present highly efficient electroluminescent devices using size-separated silicon nanocrystals (ncSi) as light emitting material. The emission color can be tuned from the deep red down to yellow-orange spectral region by very monodisperse nanoparticles. High external quantum efficiencies up 1.1% well low turn-on voltages are obtained for emitters. In addition, we demonstrate that size-separation of ncSi leads drastically improved lifetimes and much less sensitivity wavelength applied drive voltage.

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Indium gallium nitride-based ultraviolet, blue, and green light-emitting diodes functionalized with shallow periodic hole patterns

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Indium gallium nitride-based ultraviolet, blue, and green light-emitting diodes functionalized with shallow periodic hole patterns by Hyun Jeong, Rafael Salas-Montiel, Gilles Lerondel, Mun Seok Jeong.

In this study, we investigated the improvement in light output power of indium gallium nitride (InGaN)-based ultraviolet (UV), blue, and green light-emitting diodes (LEDs) by fabricating shallow periodic hole patterns (PHPs) on LED surface through laser interference lithography inductively coupled plasma etching. Noticeably, different enhancements were observed powers UV, LEDs with negligible changes electrical properties versus current voltage curves. addition, confocal scanning electroluminescence microscopy is employed to verify correlation between enhancement PHPs carrier localization InGaN/GaN multiple quantum wells. Light propagation simulated using a three-dimensional finite-difference time-domain method confirm experimental results. Finally, suggest optimal conditions for improving InGaN based theoretical

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Optimizing spherical light-emitting diode array for highly uniform illumination distribution by employing genetic algorithm

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Optimizing spherical light-emitting diode array for highly uniform illumination distribution by employing genetic algorithm by Yanxia Shen, Zhicheng Ji, Zhouping Su.

A numerical optimization method (genetic algorithm) is employed to design the spherical light-emitting diode (LED) array for highly uniform illumination distribution. An evaluation function related nonuniformity constructed optimization. With minimum of function, LED produces best uniformity. The genetic algorithm used seek function. By this method, we two arrays. In one case, LEDs are positioned symmetrically on sphere and illuminated target surface a plane. However, in other nonsymmetrically with surface. Both symmetrical nonsymmetrical arrays generate good distribution calculated nonuniformities 6 8%, respectively.

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Color-Tunable and Phosphor-Free White-Light Multilayered Light-Emitting Diodes

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Color-Tunable and Phosphor-Free White-Light Multilayered Light-Emitting Diodes by Y. F. Cheung, Hoi Wai Choi.

A tightly integrated 3-D RGB light-emitting diode (LED) stack is demonstrated. Chips of identical dimensions are stacked on top each other, with wire bonds embedded within. This achieved by integrating laser-micromachined channels onto the sapphire face InGaN LEDs, serving to accommodate from chip beneath. The resultant structure eliminates leakage monochromatic light individual chips, producing optimally mixed emission through aperture. device can emit a wide range colors and an efficient phosphor-free white-light LED as well. When emitting at correlated color temperatures (CCTs) 2362 K, 5999 7332 generates ~ 20 lm/W, exhibiting performance invariant CCT. Thermal characteristics this multilayered investigated via infrared thermometry.

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Improving carrier transport and light emission in a silicon-nanocrystal based MOS light-emitting diode on silicon nanopillar array

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Improving carrier transport and light emission in a silicon-nanocrystal based MOS light-emitting diode on silicon nanopillar array by Gong-Ru Lin, Chun-Jung Lin, Hao-Chung Kuo.

A silicon-nanocrystal (nc-Si) based metal-oxide-semiconductor light-emitting diode (MOSLED) on Si nanopillar array with size, height, and density of 30nm, 350nm, 2.8×1010cm−2, respectively, is characterized. The roughened surface contributes to the improved turn-on characteristics by enhancing Fowler-Nordheim tunneling reducing effective barrier providing MOSLED a maximum optical power 0.7μW obtained at biased current 375μA. intensity, current, power-current slope nc-Si high-aspect-ratio are 140μW∕cm2, 5μA, 2±0.8mW∕A, respectively. external quantum efficiency 0.1% reported.

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