Comparison of InGaN-Based LEDs Grown on Conventional Sapphire and Cone-Shape-Patterned Sapphire Substrate

Lee, Jae‐Hoon; Lee, Dong-Yul; Oh, Bang-Won; Lee, Jung‐Hee

doi:10.1109/ted.2009.2034495

Cited by 100 publications

(49 citation statements)

References 26 publications

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“…[1][2][3][4][5][6][7][8][9][10] The improvement obtained using the patterned-sapphire substrate (PSS) technique includes the enhancements of both the internal quantum efficiency (IQE) and light extraction efficiency (LEE). The LEE is enhanced because of the patterns on the PSS act to destroy the TIR (Total Internal Reflection) effect at the GaN/sapphire interface.…”

mentioning

confidence: 99%

Pattern-Coverage Effect on Light Extraction Efficiency of GaN LED on Patterned-Sapphire Substrate

Lin

Chen

Chang

et al. 2012

Electrochem. Solid-State Lett.

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GaN-based LEDs were fabricated on patterned-sapphire substrates with various pyramidal-pattern coverage percentages (31-81%). Three distinguish stages are observed in the behavior of the light out-put power against coverage percentage. By etching-pit density measurement, dislocation density is found to be independent with coverage percentage. The light extraction efficiency (LEE) should be the main mechanism for the enhancement in the light out-put power. LEE would be enhanced, when the pattern coverage is less than 39% or over 67%. The light extraction efficiency remains similar, when the pattern coverage in between 39% ∼ 67%.The sapphire substrate patterning technique has been widely used to improve the external quantum efficiency (EQE) of GaN-based LEDs. 1-10 The improvement obtained using the patterned-sapphire substrate (PSS) technique includes the enhancements of both the internal quantum efficiency (IQE) and light extraction efficiency (LEE). The LEE is enhanced because of the patterns on the PSS act to destroy the TIR (Total Internal Reflection) effect at the GaN/sapphire interface. 1, 3, 4 Several published literatures have pointed out that the light extraction efficiency could be increased by using periodic or non-periodic micron-sized patterning on sapphire substrate. 11-16 On the other hand, the patterns on the PSS can reduce the threading dislocations in the GaN epitaxial layers owing to the possible lateral growth of the GaN epi-layer. 2,5,6,8,17 Some recent studies indicated that the use of nano-scale patterned sapphire substrate leads to increase in IQE, which is resulted from the significant reduction in the threading dislocation density (two-orders of magnitude reduction) and reduction in the fraction of the screw dislocation density. 18-21 Besides, some researchers also indicate that IQE can be improved by QW designing (for examples, non-polar QW and large overlap QW). [22][23][24][25][26][27][28][29] Generally, it seems that the greater the pattern coverage created on the PSS, the higher the LEE would be. 30 However, there so far been no any experimental study or systematically investigation of the effect of the pattern coverage of the PSS on the and LEE. Another key issue that is not yet well understood is how does the pattern coverage (or c-plane coverage) influence the IQE of a GaN-based LED on the PSS. In this study, a mask-free wet-etching process is used to produce a so-called naturally patterned-sapphire substrate (n-pss). 31 By varying the etching time and temperature, different amount of pyramidal pattern coverage can be created on the n-pss wafers. The effect of the pyramidal pattern coverage on the IQE and LEE of the GaN epi-layers can be studied.The mask-free wet-etching process used to produce the pyramidal n-pss wafers is described in detail below. Before the wet-etching process, a PECVD (Plasma Enhanced Chemical Vapor Deposition) SiO 2 layer was deposited on the back-side of the c-plane sapphire wafers to prevent the back-side of sapphire wafers from being etched. The flat back-...

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mentioning

confidence: 99%

Pattern-Coverage Effect on Light Extraction Efficiency of GaN LED on Patterned-Sapphire Substrate

Lin

Chen

Chang

et al. 2012

Electrochem. Solid-State Lett.

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“…InGaN LEDs are attractive for optogenetic applications because the emission wavelength can be tailored for the activation of common opsins 172 . GaN-based LEDs are most commonly grown on sapphire or SiC substrates for minimal lattice mismatch at the GaN-substrate interface 173 because this structure enables efficient electronto-photon conversion. Recently, LED arrays fabricated from a sapphire substrate have been demonstrated for optogenetics 174 .…”

Section: Mems Led Integrated Probesmentioning

confidence: 99%

State-of-the-art MEMS and microsystem tools for brain research

et al. 2017

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Mapping brain activity has received growing worldwide interest because it is expected to improve disease treatment and allow for the development of important neuromorphic computational methods. MEMS and microsystems are expected to continue to offer new and exciting solutions to meet the need for high-density, high-fidelity neural interfaces. Herein, the state-of-the-art in recording and stimulation tools for brain research is reviewed, and some of the most significant technology trends shaping the field of neurotechnology are discussed.

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“…Group III-nitride semiconductors and their ternary solid solutions are very promising materials for both short wavelength optoelectronics and power electronic devices [1][2][3][4]. The AlGaN/GaN heterostructure field effect transistors (HFETs) have a great potential for future high-frequency and high-power applications because of the intrinsic advantages of materials such as wide band gap, high breakdown voltage, and high electron peak velocity [5,6].…”

Section: Introductionmentioning

confidence: 99%

Growth and Device Performance of AlGaN/GaN Heterostructure with AlSiC Precoverage on Silicon Substrate

Lee

2014

Advances in Materials Science and Engineering

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A crack-free AlGaN/GaN heterostructure was grown on 4-inch Si (111) substrate with initial dot-like AlSiC precoverage layer. It is believed that introducing the AlSiC layer between AlN wetting layer and Si substrate is more effective in obtaining a compressively stressed film growth than conventional Al precoverage on Si surface. The metal semiconductor field effect transistor (MESFET), fabricated on the AlGaN/GaN heterostructure grown with the AlSiC layer, exhibited normally on characteristics, such as threshold voltage of −2.3 V, maximum drain current of 370 mA/mm, and transconductance of 124 mS/mm.

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Comparison of InGaN-Based LEDs Grown on Conventional Sapphire and Cone-Shape-Patterned Sapphire Substrate

Cited by 100 publications

References 26 publications

Pattern-Coverage Effect on Light Extraction Efficiency of GaN LED on Patterned-Sapphire Substrate

Pattern-Coverage Effect on Light Extraction Efficiency of GaN LED on Patterned-Sapphire Substrate

State-of-the-art MEMS and microsystem tools for brain research

Growth and Device Performance of AlGaN/GaN Heterostructure with AlSiC Precoverage on Silicon Substrate

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