The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform
Shing Chung Wang - One of the best experts on this subject based on the ideXlab platform.
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High light-extraction GaN-based vertical LEDs with double Diffuse Surfaces
IEEE Journal of Quantum Electronics, 2006Co-Authors: Ya Ju Lee, Tien Chang Lu, Hao-chung Kuo, Shing Chung WangAbstract:High light-extraction (external quantum efficiency ?40%) 465-nm GaN-based vertical light-emitting diodes (LEDs) employing double Diffuse Surfaces were fabricated. This novel LED structure includes one top transmitted Diffuse Surface and another Diffuse omnidirectional reflector (ODR) on the bottom of a LED chip. The diffusive ODR consists of a roughened p-type GaN layer, an indium-tin-oxide (ITO) low refractive index layer, and an Al layer. The Surface of the p-type GaN-layer was naturally roughened while decreasing the growth temperature to 800 �C. After flip-bonding onto a Si substrate by AuSn eutectic metal and laser lift-off processes to remove the sapphire substrate, an anisotropic etching by dilute potassium hydroxide (KOH) was employed on the N-face n-GaN layer to obtain transmitted Diffuse Surfaces with hexagonal-cone morphology. The double Diffused Surfaces LEDs show an enhancement of 56% and 236% in light output power compared to single side Diffused Surface and conventional LEDs, respectively. The devices also show a low leakage current in the order of magnitude of 10-8 A at -5 V and a calculated external quantum efficiency of about 40%. The high scattering efficiency of double Diffused Surfaces could be responsible for the enhancement in the device light output power. � 2006 IEEE.
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High Light-Extraction GaN-Based Vertical LEDs With Double Diffuse Surfaces
IEEE Journal of Quantum Electronics, 2006Co-Authors: Tien Chang Lu, Shing Chung WangAbstract:High light-extraction (external quantum efficiency ~40%) 465-nm GaN-based vertical light-emitting diodes (LEDs) employing double Diffuse Surfaces were fabricated. This novel LED structure includes one top transmitted Diffuse Surface and another Diffuse omnidirectional reflector (ODR) on the bottom of a LED chip. The diffusive ODR consists of a roughened p-type GaN layer, an indium-tin-oxide (ITO) low refractive index layer, and an Al layer. The Surface of the p-type GaN-layer was naturally roughened while decreasing the growth temperature to 800 degC. After flip-bonding onto a Si substrate by AuSn eutectic metal and laser lift-off processes to remove the sapphire substrate, an anisotropic etching by dilute potassium hydroxide (KOH) was employed on the N-face n-GaN layer to obtain transmitted Diffuse Surfaces with hexagonal-cone morphology. The double Diffused Surfaces LEDs show an enhancement of 56% and 236% in light output power compared to single side Diffused Surface and conventional LEDs, respectively. The devices also show a low leakage current in the order of magnitude of 10 -8 A at -5 V and a calculated external quantum efficiency of about 40%. The high scattering efficiency of double Diffused Surfaces could be responsible for the enhancement in the device light output power
Tien Chang Lu - One of the best experts on this subject based on the ideXlab platform.
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High light-extraction GaN-based vertical LEDs with double Diffuse Surfaces
IEEE Journal of Quantum Electronics, 2006Co-Authors: Ya Ju Lee, Tien Chang Lu, Hao-chung Kuo, Shing Chung WangAbstract:High light-extraction (external quantum efficiency ?40%) 465-nm GaN-based vertical light-emitting diodes (LEDs) employing double Diffuse Surfaces were fabricated. This novel LED structure includes one top transmitted Diffuse Surface and another Diffuse omnidirectional reflector (ODR) on the bottom of a LED chip. The diffusive ODR consists of a roughened p-type GaN layer, an indium-tin-oxide (ITO) low refractive index layer, and an Al layer. The Surface of the p-type GaN-layer was naturally roughened while decreasing the growth temperature to 800 �C. After flip-bonding onto a Si substrate by AuSn eutectic metal and laser lift-off processes to remove the sapphire substrate, an anisotropic etching by dilute potassium hydroxide (KOH) was employed on the N-face n-GaN layer to obtain transmitted Diffuse Surfaces with hexagonal-cone morphology. The double Diffused Surfaces LEDs show an enhancement of 56% and 236% in light output power compared to single side Diffused Surface and conventional LEDs, respectively. The devices also show a low leakage current in the order of magnitude of 10-8 A at -5 V and a calculated external quantum efficiency of about 40%. The high scattering efficiency of double Diffused Surfaces could be responsible for the enhancement in the device light output power. � 2006 IEEE.
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High Light-Extraction GaN-Based Vertical LEDs With Double Diffuse Surfaces
IEEE Journal of Quantum Electronics, 2006Co-Authors: Tien Chang Lu, Shing Chung WangAbstract:High light-extraction (external quantum efficiency ~40%) 465-nm GaN-based vertical light-emitting diodes (LEDs) employing double Diffuse Surfaces were fabricated. This novel LED structure includes one top transmitted Diffuse Surface and another Diffuse omnidirectional reflector (ODR) on the bottom of a LED chip. The diffusive ODR consists of a roughened p-type GaN layer, an indium-tin-oxide (ITO) low refractive index layer, and an Al layer. The Surface of the p-type GaN-layer was naturally roughened while decreasing the growth temperature to 800 degC. After flip-bonding onto a Si substrate by AuSn eutectic metal and laser lift-off processes to remove the sapphire substrate, an anisotropic etching by dilute potassium hydroxide (KOH) was employed on the N-face n-GaN layer to obtain transmitted Diffuse Surfaces with hexagonal-cone morphology. The double Diffused Surfaces LEDs show an enhancement of 56% and 236% in light output power compared to single side Diffused Surface and conventional LEDs, respectively. The devices also show a low leakage current in the order of magnitude of 10 -8 A at -5 V and a calculated external quantum efficiency of about 40%. The high scattering efficiency of double Diffused Surfaces could be responsible for the enhancement in the device light output power
Seiji Higashitani - One of the best experts on this subject based on the ideXlab platform.
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influence of Diffuse Surface scattering on the stability of superconducting phases with spontaneous Surface current generated by andreev bound states
Physical Review B, 2018Co-Authors: Nobumi Miyawaki, Seiji HigashitaniAbstract:We report a theoretical study on the phase transition between superconducting states with and without spontaneous Surface current. The phase transition takes place due to the formation of Surface Andreev bound states in unconventional superconductors. Based on the quasiclassical theory of superconductivity, we examine the influence of atomic-scale Surface roughness on the Surface phase transition temperature ${T}_{s}$. To describe the Surface effect, the boundary condition for the quasiclassical Green's function is parametrized in terms of specularity (the specular reflection probability in the normal state at the Fermi level). This boundary condition allows systematic study of the Surface effect ranging from the specular limit to the Diffuse limit. We show that Diffuse quasiparticle scattering at a rough Surface causes substantial reduction of ${T}_{s}$ in the $d$-wave pairing state of high-${T}_{c}$ cuprate superconductors. We also consider a $p$-wave pairing state in which Andreev bound states similar to those in the $d$-wave state are generated. In contrast to the $d$-wave case, ${T}_{s}$ in the $p$-wave state is insensitive to the specularity. This is because the Andreev bound states in the $p$-wave superconductor are robust against Diffuse scattering, as implied from symmetry consideration for odd-frequency Cooper pairs induced at the Surface; the $p$-wave state has odd-frequency pairs with $s$-wave symmetry, while the $d$-wave state does not.
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influence of Diffuse Surface scattering on the stability of superconducting phases with spontaneous Surface current generated by andreev bound states
arXiv: Superconductivity, 2018Co-Authors: Nobumi Miyawaki, Seiji HigashitaniAbstract:We report a theoretical study on the phase transition between superconducting states with and without spontaneous Surface current. The phase transition takes place due to the formation of Surface Andreev bound states in unconventional superconductors. Based on the quasiclassical theory of superconductivity, we examine the influence of atomic-scale Surface roughness on the Surface phase transition temperature $T_s$. To describe the Surface effect, the boundary condition for the quasiclassical Green's function is parameterized in terms of specularity (the specular reflection probability in the normal state at the Fermi level). This boundary condition allows systematic study of the Surface effect ranging from the specular limit to the Diffuse limit. We show that Diffuse quasiparticle scattering at a rough Surface causes substantial reduction of $T_s$ in the d-wave pairing state of high-$T_c$ cuprate superconductors. We also consider a p-wave pairing state in which Andreev bound states similar to those in the d-wave state are generated. In contrast to the d-wave case, $T_s$ in the p-wave state is insensitive to the specularity. This is because the Andreev bound states in the p-wave superconductor are robust against Diffuse scattering, as implied from symmetry consideration for odd-frequency Cooper pairs induced at the Surface; the p-wave state has odd-frequency pairs with s-wave symmetry, while the d-wave state does not.
Ya Ju Lee - One of the best experts on this subject based on the ideXlab platform.
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High light-extraction GaN-based vertical LEDs with double Diffuse Surfaces
IEEE Journal of Quantum Electronics, 2006Co-Authors: Ya Ju Lee, Tien Chang Lu, Hao-chung Kuo, Shing Chung WangAbstract:High light-extraction (external quantum efficiency ?40%) 465-nm GaN-based vertical light-emitting diodes (LEDs) employing double Diffuse Surfaces were fabricated. This novel LED structure includes one top transmitted Diffuse Surface and another Diffuse omnidirectional reflector (ODR) on the bottom of a LED chip. The diffusive ODR consists of a roughened p-type GaN layer, an indium-tin-oxide (ITO) low refractive index layer, and an Al layer. The Surface of the p-type GaN-layer was naturally roughened while decreasing the growth temperature to 800 �C. After flip-bonding onto a Si substrate by AuSn eutectic metal and laser lift-off processes to remove the sapphire substrate, an anisotropic etching by dilute potassium hydroxide (KOH) was employed on the N-face n-GaN layer to obtain transmitted Diffuse Surfaces with hexagonal-cone morphology. The double Diffused Surfaces LEDs show an enhancement of 56% and 236% in light output power compared to single side Diffused Surface and conventional LEDs, respectively. The devices also show a low leakage current in the order of magnitude of 10-8 A at -5 V and a calculated external quantum efficiency of about 40%. The high scattering efficiency of double Diffused Surfaces could be responsible for the enhancement in the device light output power. � 2006 IEEE.
Tomasz J Antosiewicz - One of the best experts on this subject based on the ideXlab platform.
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Diffuse Surface Scattering and Quantum Size Effects in the Surface Plasmon Resonances of Low-Carrier-Density Nanocrystals
Journal of Physical Chemistry C, 2016Co-Authors: R. Carmina Monreal, Tomasz J Antosiewicz, S. Peter ApellAbstract:The detailed understanding of the physical parameters that determine localized Surface plasmon resonances (LSPRs) is essential to develop new applications for plasmonics. A relatively new area of research has been opened by the identification of LSPRs in low-carrier-density systems obtained by doping semiconductor quantum dots. We investigate theoretically how Diffuse Surface scattering of electrons in combination with the effect of quantization due to size (QSE) impact the evolution of the LSPRs with the size of these nanosystems. Two key parameters are the length R0 giving the strength of the QSE and the velocity βT of the electronic excitations entering in the length scale for Diffuse Surface scattering. Although the QSE itself only produces a blueshift in energy of the LSPRs, the Diffuse Surface scattering mechanism gives to both energy and line width an oscillatory-damped behavior as a function of size, with characteristic lengths that depend on material parameters. Thus, the evolution of the LSPRs w...
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Diffuse Surface Scattering and Quantum Size Effects in the Surface Plasmon Resonances of Low Carrier Density Nanocrystals
arXiv: Optics, 2016Co-Authors: R. Carmina Monreal, Tomasz J Antosiewicz, S. Peter ApellAbstract:The detailed understanding of the physical parameters that determine Localized Surface Plasmon Resonances (LSPRs) is essential to develop new applications for plasmonics. A relatively new area of research has been opened by the identification of LSPRs in low carrier density systems obtained by doping semiconductor quantum dots. We investigate theoretically how Diffuse Surface scattering of electrons in combination with the effect of quantization due to size (QSE) impact the evolution of the LSPRs with the size of these nanosystems. Two key parameters are the length $R_0$ giving the strength of the QSE and the velocity $\beta_T$ of the electronic excitations entering in the length scale for Diffuse Surface scattering. While the QSE itself only produces a blueshift in energy of the LSPRs, the Diffuse Surface scattering mechanism gives to both energy and linewidth an oscillatory-damped behavior as a function of size, with characteristic lengths that depend on material parameters. Thus, the evolution of the LSPRs with size at the nanometer scale is very dependent on the relation of size to these lengths, which we illustrate with several examples. The variety of behaviors we find could be useful for designing plasmonic devices based on doped semiconductor nano structures having desired properties.
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Diffuse Surface scattering in the plasmonic resonances of ultralow electron density nanospheres
Journal of Physical Chemistry Letters, 2015Co-Authors: Carmina R Monreal, Tomasz J Antosiewicz, Peter S ApellAbstract:Localized Surface plasmon resonances (LSPRs) have recently been identified in extremely diluted electron systems obtained by doping semiconductor quantum dots. Here, we investigate the role that different Surface effects, namely, electronic spill-out and Diffuse Surface scattering, play in the optical properties of these ultralow electron density nanosystems. Diffuse scattering originates from imperfections or roughness at a microscopic scale on the Surface. Using an electromagnetic theory that describes this mechanism in conjunction with a dielectric function including the quantum size effect, we find that the LSPRs show an oscillatory behavior in both position and width for large particles and a strong blue shift in energy and an increased width for smaller radii, consistent with recent experimental results for photodoped ZnO nanocrystals. We thus show that the commonly ignored process of Diffuse Surface scattering is a more important mechanism affecting the plasmonic properties of ultralow electron density nanoparticles than the spill-out effect.
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Diffuse Surface Scattering in the Plasmonic Resonances of Ultra-Low Electron Density Nanospheres
arXiv: Optics, 2015Co-Authors: R. Carmina Monreal, Tomasz J Antosiewicz, S. Peter ApellAbstract:Localized Surface plasmon resonances (LSPRs) have recently been identified in extremely diluted electron systems obtained by doping semiconductor quantum dots. Here we investigate the role that different Surface effects, namely electronic spill-out and Diffuse Surface scattering, play in the optical properties of these ultra-low electron density nanosystems. Diffuse scattering originates from imperfections or roughness at a microscopic scale on the Surface. Using an electromagnetic theory that describes this mechanism in conjunction with a dielectric function including the quantum size effect, we find that the LSPRs show an oscillatory behavior both in position and width for large particles and a strong blueshift in energy and an increased width for smaller radii, consistent with recent experimental results for photodoped ZnO nanocrystals. We thus show that the commonly ignored process of Diffuse Surface scattering is a more important mechanism affecting the plasmonic properties of ultra-low electron density nanoparticles than the spill-out effect.