Improved Light Extraction of Nitride-Based Flip-Chip Light-Emitting Diodes Via Sapphire Shaping and Texturing

Huang, Shaohua; Horng, Ray−Hua; Wen, K. S.; Lin, Yi‐Feng; Yen, Kuo-Yi; Wuu, Dong−Sing

doi:10.1109/lpt.2006.886823

Cited by 48 publications

(17 citation statements)

References 9 publications

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“…The topography of PSS was characterized with a commercial AFM system (Bruker MultiMode 8) at ambient conditions (25 • C, 35-40% RH). All images were recorded with a calibrated J scanner in the ScanAsyst mode with special Opus 4XC probes (MikroMasch) featured with sharp tips (nominal tip radius: <7 nm, force constant of cantilever: 2.5 N/m) and vertical front slant angle.…”

Section: Methodsmentioning

confidence: 99%

AFM and SEM Study on Crystallographic and Topographical Evolution of Wet-Etched Patterned Sapphire Substrates (PSS)

Shen

Zhang

Wang

2016

ECS J. Solid State Sci. Technol.

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A thorough understanding about the crystallographic and topographical evolution of wet-etched patterned sapphire substrates (PSS) is essential for revealing the etching mechanism and critical for fabricating optimized PSS for enhanced performance of GaN-based LED devices. As the first one of a series of three papers, using complementary scanning electron microscope (SEM) and atomic force microscope (AFM), we carried out a systematic study on the crystallographic and topographical evolution of cone-shaped PSS etched with an ordinary etchant (H 2 SO 4 :H 3 PO 4 = 3:1 at volume ratio, 230 • C) which enables crystallographic specific etching. The topography of patterns was found to evolve from normal cones to truncated cones, to triangular pyramids with multiple families of exposed crystallographic planes, then to hexagonal and triangular pyramids with a single family of planes. The Miller indexes of three major exposed crystallographic planes, with decreasing slant angles, were determined to be {11 0 5}, {45 1 38} and {11 0 12} with the last two being reported for the first time to our best knowledge. It was clearly demonstrated that AFM, thanks to its 3D topography imaging capability compared to SEM and focused ion beam, can be an indispensable tool for fast and reliable characterization of routine PSS samples.

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Section: Methodsmentioning

confidence: 99%

AFM and SEM Study on Crystallographic and Topographical Evolution of Wet-Etched Patterned Sapphire Substrates (PSS)

Shen

Zhang

Wang

2016

ECS J. Solid State Sci. Technol.

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“…Owing to the index mismatch of GaN epilayer, sapphire substrate and air, the majority of photons are trapped in the high-index epilayer and sapphire substrate by total internal reflection (TIR) and guided laterally as waveguide modes, which finally dissipate in the lossy epilayer. Several methods have been proposed to extract the waveguide photons of flip-chip LEDs, such as texturing the sapphire subtract surface [16,17,18], shaping the sapphire substrate [19,20], plasmonic structure [21], and depositing nanoparticles or scattering layers [22,23]. Such approaches are effective in extraction of the sapphire substrate mode photons, while additional protection procedures are generally needed owing to the more inert property of sapphire substrate relative to the epilayer.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Light Extraction of Flip-Chip Mini-LEDs with Prism-Structured Sidewall

Tang

Jia

Liu³

et al. 2019

Nanomaterials

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Current solutions for improving the light extraction efficiency of flip-chip light-emitting diodes (LEDs) mainly focus on relieving the total internal reflection at sapphire/air interface, but such methods hardly affect the epilayer mode photons. We demonstrated that the prism-structured sidewall based on tetramethylammonium hydroxide (TMAH) etching is a cost-effective solution for promoting light extraction efficiency of flip-chip mini-LEDs. The anisotropic TMAH etching created hierarchical prism structure on sidewall of mini-LEDs for coupling out photons into air without deteriorating the electrical property. Prism-structured sidewall effectively improved light output power of mini-LEDs by 10.3%, owing to the scattering out of waveguided light trapped in the gallium nitride (GaN) epilayer.

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“…The details of this processing were reported elsewhere. 23 of bulk-GaN LEDs with a truncated-pyramidal shape was shown in Fig. 1.…”

Section: Fabricationmentioning

confidence: 99%

Shape designing for light extraction enhancement bulk-GaN light-emitting diodes

Sun

Zhao

Wei

et al. 2013

Journal of Applied Physics

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Light extraction efficiency enhancement of bulk GaN light-emitting diodes (LEDs) in the shape of truncated-pyramid has been investigated. Compared with the reference LEDs, an enhancement of up to 46% on the light output power from rectangle-shaped LEDs chip with the inclination angle ($44 ) has been observed. Compared with the common triangle-shaped and hexagon-shaped LEDs, large size of conventional rectangular LEDs shaped with truncated-pyramid shows more obvious enhancement in light extraction efficiency. In addition, the ray-tracing simulations results show that light extraction efficiency was influenced not only by inclination angle but also by dimension size. V C 2013 AIP Publishing LLC. [http://dx.

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Improved Light Extraction of Nitride-Based Flip-Chip Light-Emitting Diodes Via Sapphire Shaping and Texturing

Cited by 48 publications

References 9 publications

AFM and SEM Study on Crystallographic and Topographical Evolution of Wet-Etched Patterned Sapphire Substrates (PSS)

AFM and SEM Study on Crystallographic and Topographical Evolution of Wet-Etched Patterned Sapphire Substrates (PSS)

Enhanced Light Extraction of Flip-Chip Mini-LEDs with Prism-Structured Sidewall

Shape designing for light extraction enhancement bulk-GaN light-emitting diodes

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