The Experts below are selected from a list of 57 Experts worldwide ranked by ideXlab platform
Jong Kyu Kim - One of the best experts on this subject based on the ideXlab platform.
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Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant Emission
Light: Science & Applications, 2015Co-Authors: Dong Yeong Kim, Jun Hyuk Park, Jong Won Lee, Sunyong Hwang, Jungsub Kim, Cheolsoo Sone, E. Fred Schubert, Jong Kyu KimAbstract:A way to overcome the low light extraction efficiencies of AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) has been shown. AlGaN-based DUV LEDs are promising DUV sources, but their light-extraction efficiency drops with decreasing wavelength because of their highly anisotropic light Emission. Researchers in Korea and the United States demonstrate a strategy that exploits this characteristic. Specifically, they fabricated DUV LEDs that have light-emitting mesa stripes to efficiently extract DUV light from the AlGaN active region and reflectors between the stripes to reflect this light upward. This strategy simultaneously improves the optical and electrical properties of the DUV LEDs: they have both enhanced light output due a higher light-extraction efficiency and considerably lower operating voltages than conventional DUV LEDs. The researchers expect that the DUV LEDs can be further improved by optimizing their geometry. While the demand for deep ultraviolet (DUV) light sources is rapidly growing, the efficiency of current AlGaN-based DUV light-emitting diodes (LEDs) remains very low due to their fundamentally limited light-extraction efficiency (LEE), calling for a novel LEE-enhancing approach to deliver a real breakthrough. Here, we propose sidewall Emission-enhanced (SEE) DUV LEDs having multiple light-emitting mesa stripes to utilize inherently strong transverse-magnetic polarized light from the AlGaN active region and three-dimensional reflectors between the stripes. The SEE DUV LEDs show much enhanced light output power with a strongly upward-directed Emission due to the exposed sidewall of the active region and Al-coated selective-area-grown n-type GaN micro-reflectors. The devices also show reduced operating voltage due to better n-type ohmic contact formed on the regrown n-GaN stripes when compared with conventional LEDs. Accordingly, the proposed approach simultaneously improves optical and electrical properties. In addition, strategies to further enhance the LEE up to the theoretical optimum value and Control Emission directionality are discussed.
Dong Yeong Kim - One of the best experts on this subject based on the ideXlab platform.
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Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant Emission
Light: Science & Applications, 2015Co-Authors: Dong Yeong Kim, Jun Hyuk Park, Jong Won Lee, Sunyong Hwang, Jungsub Kim, Cheolsoo Sone, E. Fred Schubert, Jong Kyu KimAbstract:A way to overcome the low light extraction efficiencies of AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) has been shown. AlGaN-based DUV LEDs are promising DUV sources, but their light-extraction efficiency drops with decreasing wavelength because of their highly anisotropic light Emission. Researchers in Korea and the United States demonstrate a strategy that exploits this characteristic. Specifically, they fabricated DUV LEDs that have light-emitting mesa stripes to efficiently extract DUV light from the AlGaN active region and reflectors between the stripes to reflect this light upward. This strategy simultaneously improves the optical and electrical properties of the DUV LEDs: they have both enhanced light output due a higher light-extraction efficiency and considerably lower operating voltages than conventional DUV LEDs. The researchers expect that the DUV LEDs can be further improved by optimizing their geometry. While the demand for deep ultraviolet (DUV) light sources is rapidly growing, the efficiency of current AlGaN-based DUV light-emitting diodes (LEDs) remains very low due to their fundamentally limited light-extraction efficiency (LEE), calling for a novel LEE-enhancing approach to deliver a real breakthrough. Here, we propose sidewall Emission-enhanced (SEE) DUV LEDs having multiple light-emitting mesa stripes to utilize inherently strong transverse-magnetic polarized light from the AlGaN active region and three-dimensional reflectors between the stripes. The SEE DUV LEDs show much enhanced light output power with a strongly upward-directed Emission due to the exposed sidewall of the active region and Al-coated selective-area-grown n-type GaN micro-reflectors. The devices also show reduced operating voltage due to better n-type ohmic contact formed on the regrown n-GaN stripes when compared with conventional LEDs. Accordingly, the proposed approach simultaneously improves optical and electrical properties. In addition, strategies to further enhance the LEE up to the theoretical optimum value and Control Emission directionality are discussed.
Ewa Adamiec - One of the best experts on this subject based on the ideXlab platform.
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Chemical fractionation and mobility of traffic-related elements in road environments
Environmental Geochemistry and Health, 2017Co-Authors: Ewa AdamiecAbstract:Due to considerable progress in exhaust Control Emission technology and extensive regulatory work regarding this issue, non-exhaust sources of air pollution have become a growing concern. This research involved studying three types of road environment samples such as road dust, sludge from storm drains and roadside soil collected from heavily congested and polluted cities in Poland (Krakow, Warszawa, Opole and Wroclaw). Particles below 20 µm were examined since it was previously estimated that this fine fraction of road dust is polluted mostly by metals derived from non-exhaust sources of pollution such as brake linings wear. Chemical analysis of all samples was combined with a fractionation study using BCR protocol. It was concluded that the finest fractions of road environment samples were significantly contaminated with all of the investigated metals, in particular with Zn, Cu, both well-known key tracers of brake and tire wear. In Warszawa, the pollution index for Zn was on average 15–18 times the background value, in Krakow 12 times, in Wroclaw 8–12 times and in Opole 6–9 times the background value. The pollution index for Cu was on average 6–14 times the background in Warszawa, 7–8 times in Krakow, 4–6 times in Wroclaw and in Opole 5 times the background value. Fractionation study revealed that mobility of examined metals decreases in that order: Zn (43–62%) > Cd (25–42%) > Ni (6–16%) > Cu (3–14%) > Pb (1–8%). It should, however, be noted that metals even when not mobile in the environment can become a serious health concern when ingested or inhaled.
E. Fred Schubert - One of the best experts on this subject based on the ideXlab platform.
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Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant Emission
Light: Science & Applications, 2015Co-Authors: Dong Yeong Kim, Jun Hyuk Park, Jong Won Lee, Sunyong Hwang, Jungsub Kim, Cheolsoo Sone, E. Fred Schubert, Jong Kyu KimAbstract:A way to overcome the low light extraction efficiencies of AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) has been shown. AlGaN-based DUV LEDs are promising DUV sources, but their light-extraction efficiency drops with decreasing wavelength because of their highly anisotropic light Emission. Researchers in Korea and the United States demonstrate a strategy that exploits this characteristic. Specifically, they fabricated DUV LEDs that have light-emitting mesa stripes to efficiently extract DUV light from the AlGaN active region and reflectors between the stripes to reflect this light upward. This strategy simultaneously improves the optical and electrical properties of the DUV LEDs: they have both enhanced light output due a higher light-extraction efficiency and considerably lower operating voltages than conventional DUV LEDs. The researchers expect that the DUV LEDs can be further improved by optimizing their geometry. While the demand for deep ultraviolet (DUV) light sources is rapidly growing, the efficiency of current AlGaN-based DUV light-emitting diodes (LEDs) remains very low due to their fundamentally limited light-extraction efficiency (LEE), calling for a novel LEE-enhancing approach to deliver a real breakthrough. Here, we propose sidewall Emission-enhanced (SEE) DUV LEDs having multiple light-emitting mesa stripes to utilize inherently strong transverse-magnetic polarized light from the AlGaN active region and three-dimensional reflectors between the stripes. The SEE DUV LEDs show much enhanced light output power with a strongly upward-directed Emission due to the exposed sidewall of the active region and Al-coated selective-area-grown n-type GaN micro-reflectors. The devices also show reduced operating voltage due to better n-type ohmic contact formed on the regrown n-GaN stripes when compared with conventional LEDs. Accordingly, the proposed approach simultaneously improves optical and electrical properties. In addition, strategies to further enhance the LEE up to the theoretical optimum value and Control Emission directionality are discussed.
Cheolsoo Sone - One of the best experts on this subject based on the ideXlab platform.
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Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant Emission
Light: Science & Applications, 2015Co-Authors: Dong Yeong Kim, Jun Hyuk Park, Jong Won Lee, Sunyong Hwang, Jungsub Kim, Cheolsoo Sone, E. Fred Schubert, Jong Kyu KimAbstract:A way to overcome the low light extraction efficiencies of AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) has been shown. AlGaN-based DUV LEDs are promising DUV sources, but their light-extraction efficiency drops with decreasing wavelength because of their highly anisotropic light Emission. Researchers in Korea and the United States demonstrate a strategy that exploits this characteristic. Specifically, they fabricated DUV LEDs that have light-emitting mesa stripes to efficiently extract DUV light from the AlGaN active region and reflectors between the stripes to reflect this light upward. This strategy simultaneously improves the optical and electrical properties of the DUV LEDs: they have both enhanced light output due a higher light-extraction efficiency and considerably lower operating voltages than conventional DUV LEDs. The researchers expect that the DUV LEDs can be further improved by optimizing their geometry. While the demand for deep ultraviolet (DUV) light sources is rapidly growing, the efficiency of current AlGaN-based DUV light-emitting diodes (LEDs) remains very low due to their fundamentally limited light-extraction efficiency (LEE), calling for a novel LEE-enhancing approach to deliver a real breakthrough. Here, we propose sidewall Emission-enhanced (SEE) DUV LEDs having multiple light-emitting mesa stripes to utilize inherently strong transverse-magnetic polarized light from the AlGaN active region and three-dimensional reflectors between the stripes. The SEE DUV LEDs show much enhanced light output power with a strongly upward-directed Emission due to the exposed sidewall of the active region and Al-coated selective-area-grown n-type GaN micro-reflectors. The devices also show reduced operating voltage due to better n-type ohmic contact formed on the regrown n-GaN stripes when compared with conventional LEDs. Accordingly, the proposed approach simultaneously improves optical and electrical properties. In addition, strategies to further enhance the LEE up to the theoretical optimum value and Control Emission directionality are discussed.