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Hsu CH, Luo HL, Li ST, Bian FQ, Chen YZ, Gao P, Wu WY, Wuu DS, Lai FM, Lien SY, Zhu WZ. Internal moisture barrier layer for improving high-humidity reliability of miniature light emitting diode die without encapsulation. OPTICS EXPRESS 2023; 31:33732-33740. [PMID: 37859146 DOI: 10.1364/oe.499380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 09/06/2023] [Indexed: 10/21/2023]
Abstract
Atomic layer deposited Al2O3 films are incorporated into miniature light emitting diodes (mini-LEDs) as an internal moisture barrier layer. The experimental results show that the water vapor transmission rate reaches ≤10-4 g/m2/day when the Al2O3 thickness is ≥40 nm. The mini-LED with a 40 nm-thick Al2O3 layer shows negligible degradation after 1000 h of 85°C/85% relative humidity testing, whereas the device without an Al2O3 layer fails after only 500 h due to delamination occurring at the GaN surface. Current-voltage characteristics of the device without an Al2O3 moisture barrier layer indicate an increase in series resistance and ideality factor. This study provides a simple, light-weighting method to have a satisfactory encapsulation function for miniature LEDs.
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2
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Li X, Li L, Wang Y, Hao X, Wang C, Yang Z, Li H. Ag NPs@PDMS nanoripple array films as SERS substrates for rapid in situ detection of pesticide residues. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 299:122877. [PMID: 37209479 DOI: 10.1016/j.saa.2023.122877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 05/06/2023] [Accepted: 05/10/2023] [Indexed: 05/22/2023]
Abstract
The large-area fabrication of flexible and transparent surface-enhanced Raman scattering (SERS) substrates with high performance by a facile and efficient method is still challenging. Here, we demonstrated a large-scale, flexible and transparent SERS substrate composed of PDMS nanoripple array film decorated with silver nanoparticles (Ag NPs@PDMS-NR array film) prepared by a combination of plasma treatment and magnetron sputtering. The performances of SERS substrates were characterized by rhodamine 6G (R6G) using a handheld Raman spectrometer. The optimal Ag NPs@PDMS-NR array film exhibited high SERS sensitivity, with a detection limitation of R6G reaching 8.20 × 10-8 M as well as excellent uniformity (RSD = 6.8%) and batch-to-batch reproducibility (RSD = 2.3%). In addition, the substrate showed outstanding mechanical stability and good SERS enhancement by backside illumination, thus it was suitable for in situ SERS detection on curved surfaces. The detection limit of malachite green on apple and tomato peels was 1.19 × 10-7 and 1.16 × 10-7 M, respectively, and quantitative analysis of pesticide residues could be realized. These results demonstrate that the Ag NPs@PDMS-NR array film has great practical potential in rapid in situ detection of pollutants.
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Affiliation(s)
- Xiaojian Li
- School of Physical Science and Information Technology, Key Laboratory of Optical Communication Science and Technology of Shandong Province, Liaocheng University, Liaocheng 252000, PR China
| | - Lijun Li
- School of Physical Science and Information Technology, Key Laboratory of Optical Communication Science and Technology of Shandong Province, Liaocheng University, Liaocheng 252000, PR China
| | - Yangzhi Wang
- School of Physical Science and Information Technology, Key Laboratory of Optical Communication Science and Technology of Shandong Province, Liaocheng University, Liaocheng 252000, PR China
| | - Xuehui Hao
- School of Materials Science and Engineering, Liaocheng University, Liaocheng 252000, PR China
| | - Changzheng Wang
- School of Materials Science and Engineering, Liaocheng University, Liaocheng 252000, PR China
| | - Zhenshan Yang
- School of Physical Science and Information Technology, Key Laboratory of Optical Communication Science and Technology of Shandong Province, Liaocheng University, Liaocheng 252000, PR China
| | - Hefu Li
- School of Physical Science and Information Technology, Key Laboratory of Optical Communication Science and Technology of Shandong Province, Liaocheng University, Liaocheng 252000, PR China.
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3
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Park AH, Baek S, Kim YW, Chandramohan S, Suh EK, Seo TH. Defect-selective-etched porous GaN as a buffer layer for high efficiency InGaN/GaN light-emitting diodes. PLoS One 2022; 17:e0277667. [PMCID: PMC9671350 DOI: 10.1371/journal.pone.0277667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 11/01/2022] [Indexed: 11/19/2022] Open
Abstract
Substrate-induced biaxial compressive stress and threading dislocations (TDs) have been recognized to severely impair the performance, stability, and reliability of InGaN/GaN light-emitting diodes (LEDs) for quite some time. In this study, a defect-selective-etched (DSE) porous GaN layer is fabricated employing electro-chemical etching and applied as a buffer layer for the development of InGaN/GaN LEDs with high quantum efficiency. Based on the analysis of photoluminescence and micro-Raman spectra, it has been revealed that the overgrown GaN epilayer on the DSE porous GaN has a relatively low TDs and relaxation of compressive stress in comparison to the conventional GaN epilayer. The remarkable improvement in the internal quantum efficiency of the InGaN/GaN LEDs is directly attributable to the strong radiative recombination in InGaN/GaN multi-quantum-wells caused by stress relaxation and TDs annihilation. Our findings indicate that the use of DSE porous GaN as a buffer layer may be a viable approach for producing crystalline GaN epilayers and high-performance LEDs.
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Affiliation(s)
- Ah Hyun Park
- R&D Center, Marine Equipment Technology Solutions, Busan, Republic of Korea
| | - Seungjae Baek
- Maritime ICT R&D Center, Korea Institute of Ocean Science and Technology, Busan, Republic of Korea
| | - Young Won Kim
- Green Energy & Nano Technology R&D Group, Korea Institute of Industrial Technology, Gwangju, Republic of Korea
| | - S. Chandramohan
- Department of Physics and Nanotechnology, SRM Institute of Science and Technology, Kattankulathur, Tamil Nadu, India
- School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Jeonbuk National University, Jeonju, Republic of Korea
| | - Eun-Kyung Suh
- School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Jeonbuk National University, Jeonju, Republic of Korea
- * E-mail: (THS); (EKS)
| | - Tae Hoon Seo
- Green Energy & Nano Technology R&D Group, Korea Institute of Industrial Technology, Gwangju, Republic of Korea
- * E-mail: (THS); (EKS)
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4
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Thermophysical Characterization of Efficiency Droop in GaN-Based Light-Emitting Diodes. NANOMATERIALS 2021; 11:nano11061449. [PMID: 34070771 PMCID: PMC8227426 DOI: 10.3390/nano11061449] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 05/18/2021] [Accepted: 05/27/2021] [Indexed: 11/16/2022]
Abstract
An efficiency droop in GaN-based light-emitting diodes (LED) was characterized by examining its general thermophysical parameters. An effective suppression of emission degradation afforded by the introduction of InGaN/GaN heterobarrier structures in the active region was attributable to an increase in the capture cross-section ratios. The Debye temperatures and the electron–phonon interaction coupling coefficients were obtained from temperature-dependent current-voltage measurements of InGaN/GaN multiple-quantum-well LEDs over a temperature range from 20 to 300 K. It was found that the Debye temperature of the LEDs was modulated by the InN molar fraction in the heterobarriers. As far as the phonons involved in the electron–phonon scattering process are concerned, the average number of phonons decreases with the Debye temperature, and the electron–phonon interaction coupling coefficients phenomenologically reflect the nonradiative transition rates. We can use the characteristic ratio of the Debye temperature to the coupling coefficient (DCR) to assess the efficiency droop phenomenon. Our investigation showed that DCR is correlated to quantum efficiency (QE). The light emission results exhibited the high and low QEs to be represented by the high and low DCRs associated with low and high injection currents, respectively. The DCR can be envisioned as a thermophysical marker of LED performance, not only for efficiency droop characterization but also for heterodevice structure optimization.
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5
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Singh MR, Brassem G, Yastrebov S. Optical quantum yield in plasmonic nanowaveguide. NANOTECHNOLOGY 2021; 32:135207. [PMID: 33271522 DOI: 10.1088/1361-6528/abd05d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We have developed a theory of the quantum yield for plasmonic nanowaveguide where the cladding layer is made of an ensemble of quantum dots and the core layer consists of an ensemble of metallic nanoparticles. The bound states of the confined probe photons in the plasmonic nanowaveguide are calculated using the transfer matrix method based on the Maxwell equations. It is shown that the number of bound states in the nanowaveguide depends on the dielectric properties of the core and cladding layers. The surface plasmon polaritons (SPPs) produced by the metallic nanoparticles interacts with the excitons of the quantum dots. The radiative and nonradiative linewidths of excitons in the quantum yield are calculated using the quantum mechanical perturbation theory. We have found that the quantum yield decreases as the dipole-dipole interaction between metallic nanoparticles increases. We have also calculated the photoluminescence and found that the enhancement in photoluminescence is due to the SPPs coupling. On the other hand, the quenching in the photoluminescence is due to the quantum yield. We compared our theory with experiments of a nanowaveguide where the core is fabricated from Ag- nanoparticles and the cladding is fabricated from the perovskite quantum dots. A good agreement between theory and experiments is found. Our analytical expressions of the quantum yield and photoluminescence can be used by experimentalists to proforma new types of experiments and for inventing new types of nanosensors and nanoswitches.
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Affiliation(s)
- Mahi R Singh
- Department of Physics and Astronomy, The University of Western Ontario, London N6A 3K7, Canada
| | - Grant Brassem
- Department of Physics and Astronomy, The University of Western Ontario, London N6A 3K7, Canada
| | - Sergey Yastrebov
- F.Ioffe Physical-Technical Institute Laboratory of Electrical and Optical Phenomena in Semiconductors St. Petersburg, 194021, Russia
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6
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Park JY, Kim BJ, Yoo CJ, Dong WJ, Lee I, Kim S, Lee JL. Subwavelength-scale nanorods implemented hexagonal pyramids structure as efficient light-extraction in Light-emitting diodes. Sci Rep 2020; 10:5540. [PMID: 32218542 PMCID: PMC7098980 DOI: 10.1038/s41598-020-62257-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2019] [Accepted: 02/19/2020] [Indexed: 11/22/2022] Open
Abstract
Subwavelength-scale nanorods were implemented on the hexagonal pyramid of photochemically etched light-emitting diodes (LEDs) to improve light extraction efficiency (LEE). Sequential processes of Ag deposition and inductively coupled plasma etching successfully produce nanorods on both locally unetched flat surface and sidewall of hexagonal pyramids. The subwavelength-scale structures on flat surface offer gradually changed refractive index, and the structures on side wall of hexagonal pyramid reduce backward reflection, thereby enhancing further enhancement of the light extraction efficiency. Consequently, the nanorods implemented LED shows a remarkable enhancement in the light output power by 14% compared with that of the photochemically etched LEDs which is known to exhibit the highest light output power. Theoretical calculations using a rigorous coupled wave analysis method reveal that the subwavelength-scale nanorods are very effective in the elimination of TIR as well as backward reflections, thereby further enhancing LEE of the LEDs.
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Affiliation(s)
- Jae Yong Park
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Buem Joon Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Chul Jong Yoo
- Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Wan Jae Dong
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Illhwan Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Sungjoo Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Jong-Lam Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea.
- Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea.
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7
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Gaiser HF, Popescu R, Gerthsen D, Feldmann C. Ionic-liquid-based synthesis of GaN nanoparticles. Chem Commun (Camb) 2020; 56:2312-2315. [PMID: 31989136 DOI: 10.1039/c9cc09133e] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
GaN nanoparticles, 3-8 nm in diameter, are prepared by a microwave-assisted reaction of GaCl3 and KNH2 in ionic liquids. Instantaneously after the liquid-phase synthesis, the β-GaN nanoparticles are single-crystalline. The band gap is blue-shifted by 0.6 eV in comparison to bulk-GaN indicating quantum confinement effects. The GaN nanoparticles show intense green emission with a quantum yield of 55 ± 3%.
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Affiliation(s)
- Hannah F Gaiser
- Institut für Anorganische Chemie, Karlsruhe Institute of Technology (KIT), Engesserstrasse 15, 76131 Karlsruhe, Germany.
| | - Radian Popescu
- Laboratorium für Elektronenmikroskopie, Karlsruhe Institute of Technology (KIT), Engesserstrasse 7, 76131 Karlsruhe, Germany.
| | - Dagmar Gerthsen
- Laboratorium für Elektronenmikroskopie, Karlsruhe Institute of Technology (KIT), Engesserstrasse 7, 76131 Karlsruhe, Germany.
| | - Claus Feldmann
- Institut für Anorganische Chemie, Karlsruhe Institute of Technology (KIT), Engesserstrasse 15, 76131 Karlsruhe, Germany.
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8
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Zhang J, Wang C, Wang M, Xu T. In situ synthesis of silver nanoparticles on periodic supports as highly active and flexible surface-enhanced Raman spectroscopy substrates. APPLIED OPTICS 2020; 59:662-668. [PMID: 32225192 DOI: 10.1364/ao.378734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 12/04/2019] [Indexed: 06/10/2023]
Abstract
With regard to surface-enhanced Raman spectroscopy (SERS), the preparation of substrates with high homogeneity and low cost remains a challenge. In this paper, cheap commercial DVD-R plates were adopted as supports, whose 3D periodic structure was transferred onto the surface of flexible polydimethylsiloxane (PDMS) easily. Then, silver nanoparticles were grown both on DVD and PDMS substrates by the in situ reduction method, and the SERS performances of these two substrates were investigated. The results confirmed that the PDMS-based substrate exhibited better enhancement performance and higher uniformity (RSD=4.16%). In addition, due to the flexibility and transparency of PDMS, it is not restricted by the surface shape of the object when applied in in situ detection. This low-cost, simple method will be widely used in the in situ detection of surfaces of objects of any shape.
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9
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Light Extraction Enhancement of InGaN Based Micro Light-Emitting Diodes with Concave-Convex Circular Composite Structure Sidewall. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9173458] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We demonstrate that the concave-convex circular composite structure sidewall prepared by inductively coupled plasma (ICP) etching is an effective approach to increase the light efficiency without deteriorating the electrical characteristics for micro light-emitting diodes (LEDs). The saturated light output power of the device using the concave-convex circular composite structure sidewalls with a radius of 2 μm is 39.75 mW, an improvement of 7.2% compared with that of the device using flat sidewalls. The enhanced light output characteristics are primarily attributed to the increased photon emitting due by decreasing the total internal reflection without losing the active region area.
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10
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Choi HJ, Kim S, Chu EK, Noh BR, Lee WS, Kwon SH, Oh S, Kim KK. Enhanced Photon Emission Efficiency Using Surface Plasmon Effect of Pt Nanoparticles in Ultra-Violet Emitter. MICROMACHINES 2019; 10:mi10080528. [PMID: 31405059 PMCID: PMC6722722 DOI: 10.3390/mi10080528] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 08/02/2019] [Accepted: 08/07/2019] [Indexed: 12/02/2022]
Abstract
We demonstrate the surface plasmon (SP)-enhanced ultraviolet (UV) emitter using Pt nanoparticles (NPs). The UV emitter is hole-patterned on the p-AlGaN layer to consider the penetration depth of Pt NPs. The Pt NPs with sizes under 50 nm are required to realize the plasmonic absorption in UV wavelength. In this study, we confirm the average Pt NP sizes of 10 nm, 20 nm, and 25 nm, respectively, at an annealing temperature of 600 °C. The absorption of annealed Pt NPs is covered with the 365-nm wavelength. The electroluminescence intensity of SP-UV is 70% higher than that of reference UV emitter without hole-patterns and Pt NPs. This improvement can be attributed to the increase of spontaneous emission rate through resonance coupling between the excitons in multiple quantum wells and Pt NPs deposited on the p-AlGaN layer.
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Affiliation(s)
- Hee-Jung Choi
- Department of Advanced Convergence Technology, and Research Institute of Advanced Convergence Technology, Korea Polytechnic University, 237 Sangidaehak-ro, Siheung-si 15073, Korea
| | - Sohyeon Kim
- Department of Advanced Convergence Technology, and Research Institute of Advanced Convergence Technology, Korea Polytechnic University, 237 Sangidaehak-ro, Siheung-si 15073, Korea
| | - Eun-Kyung Chu
- Department of Advanced Convergence Technology, and Research Institute of Advanced Convergence Technology, Korea Polytechnic University, 237 Sangidaehak-ro, Siheung-si 15073, Korea
| | - Beom-Rae Noh
- Department of Advanced Convergence Technology, and Research Institute of Advanced Convergence Technology, Korea Polytechnic University, 237 Sangidaehak-ro, Siheung-si 15073, Korea
| | - Won-Seok Lee
- Department of Advanced Convergence Technology, and Research Institute of Advanced Convergence Technology, Korea Polytechnic University, 237 Sangidaehak-ro, Siheung-si 15073, Korea
| | - Soon-Hwan Kwon
- Department of Advanced Convergence Technology, and Research Institute of Advanced Convergence Technology, Korea Polytechnic University, 237 Sangidaehak-ro, Siheung-si 15073, Korea
| | - Semi Oh
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor,MI 48109, USA.
| | - Kyoung-Kook Kim
- Department of Advanced Convergence Technology, and Research Institute of Advanced Convergence Technology, Korea Polytechnic University, 237 Sangidaehak-ro, Siheung-si 15073, Korea.
- Department of Nano-optical engineering, Korea Polytechnic University, 237 Sangidaehak-ro,Siheung-si 15073, Korea.
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11
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Lesage A, Timmerman D, Inaba T, Gregorkiewicz T, Fujiwara Y. Enhanced light extraction efficiency of Eu-related emission from a nano-patterned GaN layer grown by MOCVD. Sci Rep 2019; 9:4231. [PMID: 30862946 PMCID: PMC6414605 DOI: 10.1038/s41598-019-40971-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 02/25/2019] [Indexed: 11/09/2022] Open
Abstract
Eu-doped GaN is a promising material for the active layer in red light emitting diodes. Although the output power of LEDs based on GaN:Eu has been increasing by a combination of structural and growth optimizations, there is still a significant limitation resulting from a poor light extraction efficiency, typical for high refractive index materials. Here we studied nanostructuring of the top of the optical active layer by nano-cubes for enhancement of the light extraction efficiency, and its effect on the optical emission characteristics. By etching nano-cubes into the active layer, we observed an increase in directional light output power of Eu3+ ions of up to 60%, as well as a grating effect. Simultaneously, the absorption of excitation light into the optical active layer was improved, leading to a 12.8 times increase of output power per available Eu3+ ion.
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Affiliation(s)
- A Lesage
- Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - D Timmerman
- Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands. .,Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
| | - T Inaba
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - T Gregorkiewicz
- Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.,Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Y Fujiwara
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
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12
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Tuning the Resonant Frequency of a Surface Plasmon by Double-Metallic Ag/Au Nanoparticles for High-Efficiency Green Light-Emitting Diodes. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9020305] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Currently, the internal quantum efficiency (IQE) of GaInN-based green light-emitting diodes (LEDs) is still low. To overcome this problem, surface plasmon (SP)-enhanced LEDs have been intensively studied for the last 15 years. For an SP effect in green LEDs, Au and Ag are typically employed as the plasmonic materials. However, the resonance wavelength is determined by their material constants, which are theoretically fixed at ~537 nm for Au and ~437 nm for Ag. In this study, we aimed to tune the SP resonant wavelength using double-metallic nanoparticles (NPs) composed of Au and Ag to match the SP resonance wavelength to the LED emission wavelength to consequently improve the IQE of green LEDs. To form double-metallic NPs, Au/Ag multilayers were deposited on a GaN layer and then thermally annealed. We changed the thicknesses of the multilayers to control the Ag/Au ratio in the NPs. We show that the SP resonant wavelength could be tuned using our approach. We also demonstrate that the enhancement of the IQE in SP-enhanced LEDs was strongly dependent on the SP resonant wavelength. Finally, the highest IQE was achieved by matching the SP resonant wavelength to the LED emission wavelength.
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13
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Muhammed MM, Xu J, Wehbe N, Roqan IS. Carrier dynamics of In xGa 1-xN/GaN multiple quantum wells grown on (-201) β-Ga 2O 3 for bright vertical light emitting diodes. OPTICS EXPRESS 2018; 26:14869-14878. [PMID: 30114792 DOI: 10.1364/oe.26.014869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 04/16/2018] [Indexed: 06/08/2023]
Abstract
High-quality InxGa1-xN/GaN multi-quantum well (MQW) structures (0.05≤x≤0.13), are successfully grown on transparent and conductive (-201)-oriented β-Ga2O3 substrate. Scanning-transmission electron microscopy and secondary ion mass spectrometry (SIMS) show well-defined high quality MQWs, while the In and Ga compositions in the wells and the barriers are estimated by SIMS. Temperature-dependant Photoluminescence (PL) confirms high optical quality with a strong bandedge emission and negligble yellow band. time-resolved PL measurements (via above/below-GaN bandgap excitations) explain carrier dynamics, showing that the radiative recombination is predominant. Our results demonstrate that (-201)-oriented β-Ga2O3 is a strong candidate as a substrate for III-nitride-based vertical- emitting devices.
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14
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Wang W, Zheng Y, Zhang X, Li Y, Lu Z, Li G. Design and epitaxial growth of quality-enhanced crack-free GaN films on AlN/Al heterostructures and their nucleation mechanism. CrystEngComm 2018. [DOI: 10.1039/c7ce01995e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The epitaxial structures of GaN films grown on AlN/Al heterostructures by pulsed laser deposition (PLD) are designed with and without an amorphous AlN layer, and quality-enhanced crack-free GaN epitaxial films are obtained.
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Affiliation(s)
- Wenliang Wang
- State Key Laboratory of Luminescent Materials and Devices
- South China University of Technology
- Guangzhou 510640
- China
- Guangdong Choicore Optoelectronics Co. Ltd
| | - Yulin Zheng
- State Key Laboratory of Luminescent Materials and Devices
- South China University of Technology
- Guangzhou 510640
- China
| | - Xiuye Zhang
- State Key Laboratory of Luminescent Materials and Devices
- South China University of Technology
- Guangzhou 510640
- China
| | - Yuan Li
- State Key Laboratory of Luminescent Materials and Devices
- South China University of Technology
- Guangzhou 510640
- China
| | - Zhenya Lu
- Department of Electronic Materials
- School of Materials Science and Engineering
- South China University of Technology
- Guangzhou 510640
- China
| | - Guoqiang Li
- State Key Laboratory of Luminescent Materials and Devices
- South China University of Technology
- Guangzhou 510640
- China
- Guangdong Choicore Optoelectronics Co. Ltd
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15
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Determination on the Coefficient of Thermal Expansion in High-Power InGaN-based Light-emitting Diodes by Optical Coherence Tomography. Sci Rep 2017; 7:14390. [PMID: 29089538 PMCID: PMC5663912 DOI: 10.1038/s41598-017-14689-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 10/16/2017] [Indexed: 11/09/2022] Open
Abstract
The coefficient of thermal expansion (CTE) is a physical quantity that indicates the thermal expansion value of a material upon heating. For advanced thermal management, the accurate and immediate determination of the CTE of packaging materials is gaining importance because the demand for high-power lighting-emitting diodes (LEDs) is currently increasing. In this study, we used optical coherence tomography (OCT) to measure the CTE of an InGaN-based (λ = 450 nm) high-power LED encapsulated in polystyrene resin. The distances between individual interfaces of the OCT images were observed and recorded to derive the instantaneous CTE of the packaged LED under different injected currents. The LED junction temperature at different injected currents was established with the forward voltage method. Accordingly, the measured instantaneous CTE of polystyrene resin varied from 5.86 × 10−5 °C−1 to 14.10 × 10−5 °C−1 in the junction temperature range 25–225 °C and exhibited a uniform distribution in an OCT scanning area of 200 × 200 μm. Most importantly, this work validates the hypothesis that OCT can provide an alternative way to directly and nondestructively determine the spatially resolved CTE of the packaged LED device, which offers significant advantages over traditional CTE measurement techniques.
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16
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Pal AK, Mohan DB. Multi-angle ZnO microstructures grown on Ag nanorods array for plasmon-enhanced near-UV-blue light emitter. NANOTECHNOLOGY 2017; 28:415707. [PMID: 28704205 DOI: 10.1088/1361-6528/aa7fb1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Metal enhanced ultraviolet light emission has been explored in ZnO/Ag hybrid structures prepared by hydrothermal growth of multi-angled ZnO nanorods on slanted Ag nanorods array fabricated by the thermal evaporation technique. Slanted Ag nanorods are realized to be the stacking of non-spherical Ag nanoparticles, resulting in asymmetric surface plasmon resonance spectra. The surface roughness of Ag nanorod array films significantly influences the growth mechanism of ZnO nanorods, leading to the formation of multi-angled ZnO microflowers. ZnO/Ag hybrid structures facilitate the interfacial charge transfer from Ag to ZnO with the realization of negative shift in binding energy of Ag 3d orbitals by ∼0.8 eV. These high quality ZnO nanorods in ZnO/Ag hybrid nanostructures exhibit strong ultraviolet emission in the 383-396 nm region without broad deep level emission, which can be explained by a suitable band diagram. The metal enhanced photoluminescence is witnessed mainly due to interfacial charge transfer with its dependence on surface roughness of bottom layer Ag nanorods, number density of ZnO nanorods and diversity in the interfacial area between Ag and ZnO nanorods. The existence of strong ultraviolet light with minor blue light emission and appearance of CIE shade in strong violet-blue region by ZnO/Ag hybrid structures depict exciting possibilities towards near UV-blue light emitting devices.
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Affiliation(s)
- Anil Kumar Pal
- Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R.V. Nagar, Kalapet, Puducherry-605014, India
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High-efficiency light emission by means of exciton–surface-plasmon coupling. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2017. [DOI: 10.1016/j.jphotochemrev.2017.05.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Enhanced Performance of GaN-based Ultraviolet Light Emitting Diodes by Photon Recycling Using Graphene Quantum Dots. Sci Rep 2017; 7:7108. [PMID: 28769094 PMCID: PMC5541035 DOI: 10.1038/s41598-017-07483-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 06/27/2017] [Indexed: 11/12/2022] Open
Abstract
Graphene quantum dots (GQDs) with an average diameter of 3.5 nm were prepared via pulsed laser ablation. The synthesized GQDs can improve the optical and electrical properties of InGaN/InAlGaN UV light emitting diodes (LEDs) remarkably. An enhancement of electroluminescence and a decrease of series resistance of LEDs were observed after incorporation of GQDs on the LED surface. As the GQD concentration is increased, the emitted light (series resistance) in the LED increases (decreases) accordingly. The light output power achieved a maximum increase as high as 71% after introducing GQDs with the concentration of 0.9 mg/ml. The improved performance of LEDs after the introduction of GQDs is explained by the photon recycling through the light extraction from the waveguide mode and the carrier transfer from GQDs to the active layer.
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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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