Enhancement of Flip-Chip Light-Emitting Diodes With Omni-Directional Reflector and Textured Micropillar Arrays

Lee, Chia-En; Lee, Yi-Jiun; Kuo, Hao‐Chung; Tsai, Ming-Tsung; Cheng, B. S.; Lu, Tien−Chang; Wang, Shing-Chung; Kuo, Chen–Lung

doi:10.1109/lpt.2007.901718

Cited by 25 publications

(14 citation statements)

References 10 publications

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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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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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“…This natural lithography approach using ordered SiO 2 nanospheres as mask material is superior for large area, volume processes as it is very simple and fast compared to other methods such as imprinting, electron-beam lithography, focused-ion beam pattering and conventional photolithography [20][21][22]. Furthermore, this approach is highly reproducible, particularly compared to a photo-electro-chemical wet etch process based on a KOH solution.…”

Section: Resultsmentioning

confidence: 99%

Inductively coupled plasma etching of nano-patterned sapphire for flip-chip GaN light emitting diode applications

Kim¹,

Mastro²,

Jung³

et al. 2008

Thin Solid Films

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The flip-chip configuration is employed for the production of high-brightness GaN-based light emitting diodes to improve the extraction of heat. A lithographic approach based on a sacrificial SiO 2 nanosphere etch mask was developed to enhance the external extraction of light from the sapphire substrate. Closed-packed arrays of SiO 2 nanospheres were prepared by a simple solution-based method on the sapphire substrate. Subsequent dry-etching via inductively coupled plasma using a gas mixture of BCl 3 and Cl 2 transferred a pattern into the sapphire substrate with the lowest etching at the center of the SiO 2 nanosphere. This process created an array of circular cones in the surface of the sapphire that were found to be effective in enhancing the light extraction efficiency through multi-photon scatterings. Room temperature photoluminescence exhibited an increase of 22.5% in intensity after the surface of sapphire was textured.

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“…[ 127 ] FCLEDs usually use thick emission window layer, and the index difference between the sapphire substrate ( n = 1.7) and the air is much smaller than GaN. [ 128 ] There are also methods such as using photonic crystals, [ 129 ] plasmonic nanostructures, [ 130 ] micro‐pillar arrays, [ 131 ] and rough surfaces. [ 132 ] The light out‐coupling methods for commercial LEDs are quite generic and can be used for PeLEDs also.…”

Section: Light Out‐coupling Strategies For Ledsmentioning

confidence: 99%

Light Out‐Coupling Management in Perovskite LEDs—What Can We Learn from the Past?

Zhang

et al. 2020

Adv Funct Materials

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The research on perovskite light‐emitting diodes (PeLEDs) has experienced an exponential growth in the past six years. The highest external quantum efficiencies (EQEs) have surpassed 20%, 20%, and 10% for red, green, and blue colored LEDs, respectively. Considering the internal quantum efficiency is already approaching unity owing to the high material quality, the limiting factor for further improving the EQE is mainly the poor light out‐coupling efficiencies. Here, by reviewing the progress on the light out‐coupling studies for PeLEDs, organic LEDs (OLEDs), conventional semiconductor LEDs, and other special LEDs, the rational design guidelines are summarized for enhancing PeLED out‐coupling. Briefly, these design guidelines include: 1) introducing nanostructures into the active layer or tuning the thickness of it to couple out the waveguide modes, 2) adding nanostructures between the active layer and transparent electrodes to couple the waveguide modes to substrate modes, 3) adding nanostructures such as nanowires to the glass substrate to couple the substrate mode to air. Essentially, these guidelines indicate that implementing nanophotonic engineering on PeLEDs is a highly promising direction to explore, so as to substantially enhance the device performance.

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Enhancement of Flip-Chip Light-Emitting Diodes With Omni-Directional Reflector and Textured Micropillar Arrays

Cited by 25 publications

References 10 publications

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

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

Inductively coupled plasma etching of nano-patterned sapphire for flip-chip GaN light emitting diode applications

Light Out‐Coupling Management in Perovskite LEDs—What Can We Learn from the Past?

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