Selective wet etching of p-GaN for efficient GaN-based light-emitting diodes

Na, Seok‐In; Ha, Ga-Young; Han, Dae-Seob; Kim, Seok-Soon; Kim, Ja‐Yeon; Lim, Jae‐Hong; Kim, Dong Joon; Min, Kyeong-Ik; Park, Seong-Ju

doi:10.1109/lpt.2006.877562

Cited by 97 publications

(22 citation statements)

References 24 publications

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“…In order to inhibit the total reflection caused due to the refractive index difference, the extraction of the light incident within the critical angle of total reflection was improved by roughing the GaN surface forming concavo-convex patterns on it as shown in Fig 6. Anisotropic wet etching with KOH solution is adopted as the way to form concavo-convex patterns on GaN surface. [5] It is known that six-sided pyramid-shaped concavo-convex patterns in which the crystal defects are at the each top could be formed by etching GaN surface with KOH solution. [6] According to the results of the numerical analysis shown in Fig.…”

Section: Light Extraction Of Packagementioning

confidence: 99%

Optical characteristics and reliability evaluation of wafer level white LED package

Kimura

Obata

Nakayama

et al. 2012

2012 IEEE 62nd Electronic Components and Technology Conference

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In this paper, we describe optical characteristics and reliability of a novel wafer level white LED (light-emitting diode) package. In this package, re-distribution wiring layer and phosphor layer could be formed in a lump by wafer level process. As a result, ultrasmall size package that is almost same size as the chip could be attained. This approach results in drastic reduction in material and process cost. We determined the package structure from the results of the numerical analysis on the thermal cycle resistance of the package after reflow soldering. The sapphire substrate is removed by laser process and the GaN layer exists between phosphor layer and encapsulation resin. Applicative light extraction was achieved by control of GaN surface roughness. In addition, it was confirmed that the package had sufficient reliability in the thermal cycle test (TCT). Consequently, this low cost package could be applicable to LED components and also the cost of them is considered to drastically decrease.

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Section: Light Extraction Of Packagementioning

confidence: 99%

Optical characteristics and reliability evaluation of wafer level white LED package

Kimura

Obata

Nakayama

et al. 2012

2012 IEEE 62nd Electronic Components and Technology Conference

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“…For the purpose of improve the light extraction efficiency by introducing a textured surface, Na et al [4] investigated the properties of the LEDs with a p-GaN textured surface. The light output power for the textured LED was increased by 29.4%, and the wall-plug efficiency was increased by 33% at an injection current of 20mA, compared to that of the non-etched LED.…”

Section: Surface Texturing /Rougheningmentioning

confidence: 99%

Enhancing the light extraction efficiency of GaN-based LEDs

Niu

et al. 2007

SPIE Proceedings

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GaN-based light-emitting diode (LED) has been widely used in recent years, and tremendous progress has been achieved in GaN-based semiconductor materials and relevant process. However, owing to the large refractive index contrast between GaN-based semiconductor materials and air, light can be easily totally internally reflected at the semiconductor/air interface, and the critical angle for light to escape from the semiconductor is small. Therefore, the light extraction efficiency for GaN-based LED is still low and needs improving. Some of the leading approaches to enhance light extraction efficiency of GaN-based LED such as surface texturing or roughening, omnidirectional reflectors, photonic crystals, laser liftoff, transparent electrode, patterned substrate and so on are introduced in detail. For each approach, how the variation in device structure or material improves the light extraction efficiency is analyzed thoroughly. At last, some of mentioned approaches that are promising are evaluated and viewed briefly.

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“…Since the refractive indices of GaN and air are 2.5 and 1, respectively, external quantum efficiency is limited to only a few percentages for conventional GaN-based LEDs. Several methods improve the output efficiency of nitride-based LEDs, such as textured surface [3][4][5], a highly transparent p-contact layer [6], proper substrate design [7], and flip-chip packaging [8]. Findings have shown enhancing light output by the light scattering layer (e.g., roughening the p-GaN or n-GaN surface, patterned substrate, etc.).…”

Section: Introductionmentioning

confidence: 99%

“…Findings have shown enhancing light output by the light scattering layer (e.g., roughening the p-GaN or n-GaN surface, patterned substrate, etc.). With a light scattering layer, photons generated in the active layer will have multiple opportunities to find the escape cone [3][4][5][6][7][8]. Scattering from the roughened top surface of the LED or/and patterned substrate thus achieves angular randomizing of photons.…”

Section: Introductionmentioning

confidence: 99%