High-efficiency InGaN-based LEDs grown on patterned sapphire substrates using nanoimprinting technology

Lee, Yeeu-Chang; Yeh, Shiang-Chih; Chou, Yen-Yu; Tsai, Pei-Jung; Pan, Jui-Wen; Chou, Hsiu-Mei; Hou, Chia‐Hung; Chang, Yung-Yuan; Chu, M. S.; Wu, Chih-Wei; Ho, Chun-Hsien

doi:10.1016/j.mee.2013.01.027

Cited by 16 publications

(8 citation statements)

References 13 publications

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“…One of the most prominent efforts focused on a patterned sapphire substrate (PSS) that results in stress relaxation of the GaN epilayers and the reduction of TD density, leading to efficiency improvement. [13][14][15][16] Other approaches, based on inclusion of p-AlGaN [17][18] or p-InGaN/AlGaN 19 electron blocking layers (EBL) above the multi-quantum-well (MQW) LED structure, were found to enhance efficiency. Additionally, incorporation of InGaN/GaN strain-relief layers, such as strainedlayer superlattices (SLSs) or low InN content layers, have been explored as a means to increase InGaN LED efficiency by suppressing built-in polarization fields in the MQW region.…”

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confidence: 99%

Generated Carrier Dynamics in V-Pit-Enhanced InGaN/GaN Light-Emitting Diode

et al. 2017

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We investigate the effects of V-pits on the optical properties of a state-of-the art highly efficient, blue InGaN/GaN multi-quantum-well (MQW) light emitting diode (LED) with high internal quantum efficiency (IQE) of > 80%. The LED is structurally enhanced by incorporating pre-MQW InGaN strainrelief layer with low InN content and patterned sapphire substrate. For comparison, a conventional (unenhanced) InGaN/GaN MQW LED (with IQE of 46%) grown under similar conditions was subjected to the same measurements. Scanning transmission electron microscopy (STEM) reveals the absence of V-pits in the unenhanced LED, whereas in the enhanced LED, V-pits with ሼ101 ത 1ሽ facets, emerging from threading dislocations (TDs) were prominent. Cathodoluminescence mapping reveals the luminescence properties near the V-pits, showing that the formation of V-pit defects can

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mentioning

confidence: 99%

Generated Carrier Dynamics in V-Pit-Enhanced InGaN/GaN Light-Emitting Diode

et al. 2017

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“…It is known that most researchers have successfully simulated light extraction in LEDs using the ray-tracing method when they considered LEDs with mixed structure sizes, i.e. some micron-sized structures and some submicron-sized, like our LEDs [14,16,17,19,20], even though they used a strict method such as the finitedifference time-domain (FDTD) method when they considered LEDs with entirely nanoscale structures. The validity for such a use of the ray-tracing method can be explained: The key point in the phenomenon of light extraction with PSSLEDs is the breaking of TIR, so that the light's nature as a ray is more conspicuously considered than as a wave.…”

Section: Resultsmentioning

confidence: 99%

“…For example, the refractive index of gallium nitride (GaN) is 2.5, and the LEE of a GaN-based LED chip with a simple rectangular shape into free space is only 4% [1,2]. Numerous approaches have been used to improve the LEE, including photon recycling [3], flip-chip configurations [4], resonant cavities [5], a transparent surface contact layer [6], sidewall treatment [7], surface roughening [8], photonic crystals [9], chip shaping [10], and patterned sapphire substrates (PSSs) [11][12][13][14]. PSSs employ arrayed patterns on the entire top surface of the sapphire that forms the LED substrate.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulations of the Light-Extraction Efficiency of LEDs on Sapphire Substrates Patterned with Various Polygonal Pyramids

Cui

Park

2014

Journal of the Optical Society of Korea

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We report a numerical analysis of the light-extraction efficiency (LEE) of light-emitting diodes (LEDs) on patterned sapphire substrates (PSSs). We considered various n-sided, regular convex pyramids, where n is an integer and n ≥ 3. We then considered four cross sections: extruded, subtracted, truncated-extruded, and truncated-subtracted. Ray-tracing simulations were carried out with these polygonal pyramid patterns, and the dimensions of the patterns were systematically varied. Optimized pattern shapes were determined for large LEE. An extruded circular pyramid with a slant angle of 45° was found to be the optimal patterned shape.

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“…When light emits from the active layer, a very large part will propagate backward directly to the sapphire substrate. Thus, to increase the escaping opportunity from the LED chip, patterned sapphire substrate offers a promising solution since it can break the TIR and increase the LEE [57]. Zhang et al…”

Section: Patterned Sapphire Substrate (Pss)mentioning

confidence: 99%

Heat and fluid flow in high-power LED packaging and applications

Luo

Qiu

Liu

et al. 2016

Progress in Energy and Combustion Science

412

121

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Light-emitting diodes (LEDs) are widely used in our daily lives. Both light and heat are generated from LED chips and then transmitted or conducted through multiple packaging materials and interfaces. Part of the transmitted light converts into heat along the light propagation; in return, the accumulation of heat leads to the degradation of light output. The accumulated heat negatively influences the reliability and longevity of LEDs, and thus thermal management is critical for LED packaging and applications. On the other hand, in LED packaging processes, many fluid flow problems exist, such as phosphor coating, silicone injection, chip bonding, solder reflow, etc. Amongst them, phosphor coating is the most important process which is essential for LED performance. Phosphor gel is a kind of non-Newton fluid and its coating process is a typical fluid-flow problem. Overall, since LED packaging and applications present many heat and fluid flow problems, obtaining a full understanding of these problems enables advancements in the development of LED processes and designs. In this review, the emphasis is placed on heat generation in chips, heat flow in packages and application products, fluid flow in phosphor coating process, etc. This is a domain in which significant progress has been achieved in the last decade, and reporting on these advances will facilitate state-of-the-art LED packaging and application technologies.

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High-efficiency InGaN-based LEDs grown on patterned sapphire substrates using nanoimprinting technology

Cited by 16 publications

References 13 publications

Generated Carrier Dynamics in V-Pit-Enhanced InGaN/GaN Light-Emitting Diode

Generated Carrier Dynamics in V-Pit-Enhanced InGaN/GaN Light-Emitting Diode

Numerical Simulations of the Light-Extraction Efficiency of LEDs on Sapphire Substrates Patterned with Various Polygonal Pyramids

Heat and fluid flow in high-power LED packaging and applications

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