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Khan MA, Chen H, Qu J, Trimby PW, Moody S, Yao Y, Ringer SP, Zheng R. Insights into the Silver Reflection Layer of a Vertical LED for Light Emission Optimization. ACS APPLIED MATERIALS & INTERFACES 2017; 9:24259-24272. [PMID: 28653527 DOI: 10.1021/acsami.7b04854] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this work, Ag as a highly reflective mirror layer of gallium nitride (GaN)-based blue vertical light-emitting diodes (VLEDs) has been systematically investigated by correlating scanning electron microscopy/energy dispersive X-ray spectroscopy/transmission Kikuchi diffraction/electron backscatter diffraction, aberration-corrected scanning transmission electron microscopy, and atomic force microscopy techniques. In the context of high-efficiency lighting, three critical aspects have been scrutinized on the nanoscale: (1) chemical diffusion, (2) grain morphology, and (3) surface topography of the Ag layer. We found that nanoscale inhomogeneous distribution of In in InGaN/GaN quantum wells (QWs), interfacial diffusion (In/Ga out-diffusion into the Ag layer and diffusion of Ag into p-GaN and QWs), and Ag agglomeration deteriorate the light reflectivity, which account for the decreased luminous efficiency in VLEDs. Meanwhile, the surface morphology and topographical analyses revealed the nanomorphology of the Ag layer, where a nanograin size of ∼300 nm with special nanotwinned boundaries and an extremely smooth surface of ∼3-4 nm are strongly desired for better reflectivity. Further, on the basis of these microscopy results, suggestions on light extraction optimization are given to improve the performance of GaN-based blue VLEDs. Our findings enable fresh and deep understanding of performance-microstructure correlation of LEDs on the nanoscale, providing guidance to the design and manufacture of high-performance LED devices.
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Affiliation(s)
| | | | | | | | | | - Yin Yao
- Electron Microscope Unit, University of New South Wales , Sydney, New South Wales 2052, Australia
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Jeong H, Jeong HJ, Oh HM, Hong CH, Suh EK, Lerondel G, Jeong MS. Carrier localization in In-rich InGaN/GaN multiple quantum wells for green light-emitting diodes. Sci Rep 2015; 5:9373. [PMID: 25792246 PMCID: PMC4366764 DOI: 10.1038/srep09373] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/02/2015] [Indexed: 11/30/2022] Open
Abstract
Carrier localization phenomena in indium-rich InGaN/GaN multiple quantum wells (MQWs) grown on sapphire and GaN substrates were investigated. Temperature-dependent photoluminescence (PL) spectroscopy, ultraviolet near-field scanning optical microscopy (NSOM), and confocal time-resolved PL (TRPL) spectroscopy were employed to verify the correlation between carrier localization and crystal quality. From the spatially resolved PL measurements, we observed that the distribution and shape of luminescent clusters, which were known as an outcome of the carrier localization, are strongly affected by the crystalline quality. Spectroscopic analysis of the NSOM signal shows that carrier localization of MQWs with low crystalline quality is different from that of MQWs with high crystalline quality. This interrelation between carrier localization and crystal quality is well supported by confocal TRPL results.
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Affiliation(s)
- Hyun Jeong
- 1] Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Republic of Korea [2] Laboratoire de Nanotechnologie et d'Instrumentation Optique, Institut Charles Delaunay, CNRS-UMR 6281, Université de Technologie de Troyes, BP 2060, 10010 Troyes, France
| | - Hyeon Jun Jeong
- 1] Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Republic of Korea [2] Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
| | - Hye Min Oh
- 1] Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Republic of Korea [2] Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
| | - Chang-Hee Hong
- School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Eun-Kyung Suh
- School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Gilles Lerondel
- 1] Laboratoire de Nanotechnologie et d'Instrumentation Optique, Institut Charles Delaunay, CNRS-UMR 6281, Université de Technologie de Troyes, BP 2060, 10010 Troyes, France [2] Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
| | - Mun Seok Jeong
- 1] Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Republic of Korea [2] Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea
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