Development of high efficiency GaN-based multiquantum-well light-emitting diodes and their applications

Koike, Masayoshi; Shibata, Naoki; Kato, H.; Takahashi, Yasuhiko

doi:10.1109/2944.999180

Cited by 196 publications

(90 citation statements)

References 14 publications

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“…1,2 With the breakthrough of the patterned-sapphire substrate technique, the efficacy of high-brightness GaN-based LEDs has been driven to a record high of 150 lm/W. 3,4 The efficacy enhancement of GaN-based LEDs with the patterned-sapphire substrate technique generally attributes to the improvement in both light extraction efficiency and internal quantum efficiency.…”

Section: Introductionmentioning

confidence: 99%

Characterization study of GaN-based epitaxial layer and light-emitting diode on nature-patterned sapphire substrate

et al. 2012

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Chemical wet etching on c-plane sapphire wafers by three etching solutions (H 3 PO 4 , H 2 SO 4 , and H 3 PO 4 /H 2 SO 4 mixing solution) was studied. Among these etching agents, the mixing H 3 PO 4 /H 2 SO 4 solution has the fastest etching rate (1.5 lm/min). Interestingly, we found that H 2 SO 4 does not etch the c-plane sapphire wafer in thickness; instead, a facet pyramidal pattern is formed on the c-plane sapphire wafer. GaN light-emitting diode (LED) epitaxial structure was grown on the sapphire wafer with the pyramidal pattern and the standard flat sapphire wafer. X-ray diffraction and photoluminescence measurement show that the pyramidal pattern on the sapphire wafer improved crystalline quality but augmented the compressive stress level in the GaN LED epilayer. The horizontal LED chips fabricated on the pyramidal-patterned sapphire wafer have a larger light output than the horizontal LED chips fabricated on the standard flat sapphire wafer by 20%.

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Section: Introductionmentioning

confidence: 99%

Characterization study of GaN-based epitaxial layer and light-emitting diode on nature-patterned sapphire substrate

et al. 2012

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“…The poor thermal conductivities of sapphire ͑ϳ35 W/mK͒ and silver paste ͑2-25 W/mK͒ limit heat dissipation, resulting in an increased junction temperature of the device due to Joule heating. In order to enhance heat dissipation of the GaN-based LEDs for high power applications, several promising approaches have been proposed, including flip-chip packaging [2][3][4] and thin-film technology. 5 The former relies on the "sapphire-free" thermal path where generated heat can be dissipated efficiently through the contacting solders to the underlying heat sink.…”

mentioning

confidence: 99%

Thermal Management Design from Chip to Package for High Power InGaN/Sapphire LED Applications

Horng

Chiang

Tsai

et al. 2009

Electrochem. Solid-State Lett.

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Device performances were investigated for InGaN/sapphire light-emitting diodes ͑LEDs͒ with advanced heat dissipation design from chip to package. By directly contacting a copper heat spreader with sapphire, the maximum junction temperature of the LED chip was reduced from 62.9°C of a conventional LED to 48.3°C at an injection current of 350 mA. Further temperature reduction to 37.3°C could be achieved by packaging the copper-surrounded LED chip on the heat sink coated with a diamond-like layer which acts as the second heat spreader. The reduced junction temperature was attributed to good heat dissipation from both the copper and the diamond-like layer due to their low thermal resistance. The copper heat spreader not only extracts heat efficiently, but also enhances the light extraction of the LED, as the copper was designed with a proper geometry such as cup-shaped profile. The improved LED performance suggests that the proposed thermal management from chip to package is an efficient alternative for high power applications. High power GaN-based light-emitting diodes ͑LEDs͒ are essential for next-generation lighting applications. To achieve higher light output performance, it is necessary to drive a GaN-based LED to a high current density level. However, under such a high current injection, the LED typically exhibits the performance deterioration of power saturation.

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“…T HE IMPRESSIVE recent developments of highbrightness gallium nitride (GaN)-based light-emitting diodes (LEDs) have made their use in large-size flat-panel displays possible [1], [2]. However, there is still a great need to improve the internal quantum efficiency and external quantum efficiency (EQE) in order to increase the light output power and thus reduce the total cost of LED modules.…”

Section: Introductionmentioning

confidence: 99%

Improved Light Output Power of GaN-Based Light-Emitting Diodes Using Double Photonic Quasi-Crystal Patterns

Huang

Lin²,

Huang³

et al. 2009

IEEE Electron Device Lett.

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Abstract-The enhancement of light extraction from GaNbased light-emitting diodes (LEDs) with a double 12-fold photonic quasi-crystal (PQC) structure using nanoimprint lithography is presented. At a driving current of 20 mA on a transistor-outlinecan package, the light output power of an LED with a nanohole patterned sapphire substrate (NHPSS) and an LED with a double PQC structure are enhanced by 34% and 61%, compared with the conventional LED. In addition, the higher output power of the LED with the double PQC structure is due to better reflectance on NHPSS and higher scattering effect on p-GaN surface using a 12-fold PQC structure pattern. These results provide promising potential to increase the output powers of commercial lightemitting devices. Index Terms-Gallium nitride (GaN), light-emitting diodes (LEDs), nanoimprint lithography (NIL), photonic quasi-crystal (PQC).

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Development of high efficiency GaN-based multiquantum-well light-emitting diodes and their applications

Cited by 196 publications

References 14 publications

Characterization study of GaN-based epitaxial layer and light-emitting diode on nature-patterned sapphire substrate

Characterization study of GaN-based epitaxial layer and light-emitting diode on nature-patterned sapphire substrate

Thermal Management Design from Chip to Package for High Power InGaN/Sapphire LED Applications

Improved Light Output Power of GaN-Based Light-Emitting Diodes Using Double Photonic Quasi-Crystal Patterns

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