The Experts below are selected from a list of 8598 Experts worldwide ranked by ideXlab platform
Hongping Zhao - One of the best experts on this subject based on the ideXlab platform.
-
Light Extraction Efficiency enhancement for InGaN quantum wells Light-emitting diodes with GaN micro-domes
Light-Emitting Diodes: Materials Devices and Applications for Solid State Lighting XVII, 2013Co-Authors: Peng Zhao, Lu Han, Hongping ZhaoAbstract:The enhancement of Light Extraction Efficiency for thin-film-flip-chip (TFFC) InGaN QWs LEDs with GaN microdomes on n-GaN layer was studied. The three dimensional FDTD method was used to calculate the Light Extraction Efficiency for the TFFC InGaN QWs LEDs emitting at visible spectral regime, as compared to that of the conventional TFFC InGaN QWs LEDs. The calculation indicates significant dependence of the p-GaN layer thickness on the Light Extraction Efficiency. Significant enhancement of the Light Extraction Efficiency (2.5-2.7 times for λpeak=460nm and 2.7- 2.8 times for λpeak=550nm) is achievable from LEDs with GaN micro-domes with optimized micro-dome diameter and height.
-
analysis of tm mode Light Extraction Efficiency enhancement for deep ultraviolet algan quantum wells Light emitting diodes with iii nitride micro domes
Optical Materials Express, 2012Co-Authors: Peng Zhao, Lu Han, Matthew R Mcgoogan, Hongping ZhaoAbstract:Analysis of transverse magnetic (TM) mode Light Extraction Efficiency enhancement for AlGaN quantum wells (QWs) based deep ultraviolet (UV) Light-emitting diodes (LEDs) with III-nitride micro-hemisphere and micro-dome structures on the p-type layer are studied and compared to that of the conventional deep-UV LEDs with flat surface. The transverse electric (TE) and TM components of the spontaneous emission of AlGaN QWs with AlN barriers were calculated by using a self-consistent 6-band k∙p method, which shows the TM component overtakes the TE component and becomes the dominant contribution of the spontaneous emission when the Al-content of the AlGaN QWs is larger than 0.66. The TM mode Light Extraction Efficiency of the deep-UV LEDs emitting at 250 nm with AlGaN micro-domes as compared to the conventional LEDs with flat surface is calculated based on three dimensional finite difference time domain (3D-FDTD) method. The effects of the III-nitride micro-dome diameter and height as well as the p-type layer thickness on the Light Extraction Efficiency were comprehensively studied. The results indicate optimized Light Extraction Efficiency enhancement (>7.3 times) of the dominant TM polarized spontaneous emission for deep-UV LEDs with III-nitride micro-domes.
-
Analysis of Light Extraction Efficiency enhancement for thin-film-flip-chip InGaN quantum wells Light-emitting diodes with GaN micro-domes
Optics Express, 2012Co-Authors: Peng Zhao, Hongping ZhaoAbstract:The enhancement of Light Extraction Efficiency for thin-film flip-chip (TFFC) InGaN quantum wells (QWs) Light-emitting diodes (LEDs) with GaN micro-domes on n-GaN layer was studied. The Light Extraction Efficiency of TFFC InGaN QWs LEDs with GaN micro-domes were calculated and compared to that of the conventional TFFC InGaN QWs LEDs with flat surface. The three dimensional finite difference time domain (3D-FDTD) method was used to calculate the Light Extraction Efficiency for the InGaN QWs LEDs emitting at 460nm and 550 nm, respectively. The effects of the GaN micro-dome feature size and the p-GaN layer thickness on the Light Extraction Efficiency were studied systematically. Studies indicate that the p-GaN layer thickness is critical for optimizing the TFFC LED Light Extraction Efficiency. Significant enhancement of the Light Extraction Efficiency (2.5-2.7 times for λ(peak) = 460nm and 2.7-2.8 times for λ(peak) = 550nm) is achievable from TFFC InGaN QWs LEDs with optimized GaN micro-dome diameter and height.
-
Analysis of Light Extraction Efficiency enhancement for InGaN quantum wells Light-emitting diodes with microspheres
2012 IEEE Energytech, 2012Co-Authors: Peng Zhao, Xuechen Jiao, Hongping ZhaoAbstract:The enhancement of Light Extraction Efficiency for thin-film flip-chip (TFFC) InGaN quantum wells (QWs) Light-emitting diodes (LEDs) with self-assembled microspheres on top of the n-GaN layer was studied. The Light Extraction Efficiency of InGaN QWs LEDs for the three structures with 1) close-packed SiO 2 microlens; 2) close-packed SiO 2 /polystyrene microlens; and 3) GaN micro-hemispheres were calculated and compared to that of the conventional InGaN QWs LEDs with flat surface. Three dimensional finite difference time domain (3D-FDTD) method was used to calculate the Light Extraction Efficiency for TFFC InGaN/GaN QWs LEDs emitting at 460nm. The effects of the microsphere/micro-hemisphere diameter and the p-GaN layer thickness on the Light Extraction Efficiency were studied. Studies show that the p-GaN layer thickness is critical for optimizing the TFFC LED Light Extraction Efficiency. Light Extraction Efficiency enhancement of 1.7 times and 1.85 times were obtained in the TFFC LEDs with SiO 2 microlens and SiO 2 /polystyrene microlens, respectively. More significant enhancement of the Light Extraction Efficiency (>2.6 times) was achieved from LEDs with GaN micro-hemispheres with optimized micro-hemisphere diameter of D=1µm and p-GaN thickness of 195nm.
-
Optimization of Light Extraction Efficiency of III-Nitride LEDs With Self-Assembled Colloidal-Based Microlenses
IEEE Journal of Selected Topics in Quantum Electronics, 2009Co-Authors: Pisist Kumnorkaew, Hongping Zhao, Ronald A Arif, Hua Tong, James F Gilchrist, Nelson TansuAbstract:Improvement of Light Extraction Efficiency of InGaN LEDs using colloidal-based SiO2/polystyrene (PS) microlens arrays was demonstrated. The size effect of the SiO2 microspheres and the thickness effect of the PS layer on the Light Extraction Efficiency of III-nitride LEDs were studied. The monolayer rapid convective deposition conditions for SiO2 microspheres were also investigated. Ray tracing simulations show that the use of microlens arrays can lead to increase in Light Extraction Efficiency of InGaN LEDs by 2.64 times. This is consistent with experiments that demonstrated 2.49 times improvement in Light Extraction utilizing SiO2/PS microlens arrays. The enhancement in Light Extraction Efficiency is attributed to increase in effective photon escape cone due to SiO2/PS microlens arrays, and reduced Fresnel reflection within the photon escape cone due to the grading of refractive index change between GaN/SiO2/PS/air interface.
Nelson Tansu - One of the best experts on this subject based on the ideXlab platform.
-
Light Extraction Efficiency and radiation patterns of iii nitride Light emitting diodes with colloidal microlens arrays with various aspect ratios
IEEE Photonics Journal, 2011Co-Authors: Renbo Song, Pisist Kumnorkaew, James F Gilchrist, Nelson TansuAbstract:The fabrication studies of silica/polystyrene (PS) colloidal microlens arrays with various aspect ratios were performed on the III-nitride Light-emitting diodes (LEDs). The use of colloidal-based microlens arrays led to significant enhancement in Light Extraction Efficiency for III-nitride LEDs. In varying the aspect ratios of the microlens arrays, the engineering of various PS thicknesses was employed by using high-temperature treatment and redeposition process. The effects of PS thickness on the Light Extraction Efficiency and far-field emission patterns of InGaN quantum-well (QW) LEDs were studied. The total output powers of microlens LEDs with various PS thicknesses exhibited 1.93-2.70 times enhancement over that of planar LEDs, and the use of optimized PS layer thickness is important in leading the enhancement of the Light Extraction Efficiency in large angular direction.
-
Light Extraction Efficiency enhancement of ingan quantum wells Light emitting diodes with polydimethylsiloxane concave microstructures
Optics Express, 2009Co-Authors: Yikkhoon Ee, Pisist Kumnorkaew, Ronald A Arif, Hua Tong, James F Gilchrist, Nelson TansuAbstract:Improvement of Light Extraction Efficiency of InGaN Light emitting diodes (LEDs) using polydimethylsiloxane (PDMS) concave microstructures arrays was demonstrated. The size effect of the concave microstructures on the Light Extraction Efficiency of III-Nitride LEDs was studied. Depending on the size of the concave microstructures, ray tracing simulations show that the use of PDMS concave microstructures arrays can lead to increase in Light Extraction Efficiency of InGaN LEDs by 1.5 to 2.0 times. Experiments utilizing 2.0 micro n thick PDMS with 1.0 micron diameter of the PDMS concave microstructures arrays demonstrated 1.70 times improvement in Light Extraction Efficiency, which is consistent with improvement of 1.77 times predicted from simulation. The enhancement in Light Extraction Efficiency is attributed to increase in effective photon escape cone due to PDMS concave microstructures arrays.
-
Enhancement of Light Extraction Efficiency of InGaN quantum well Light-emitting diodes with polydimethylsiloxane concave microstructures
Light-Emitting Diodes: Materials Devices and Applications for Solid State Lighting XIII, 2009Co-Authors: Pisist Kumnorkaew, Ronald A Arif, Hua Tong, James F Gilchrist, Nelson TansuAbstract:Improvement of Light Extraction Efficiency of InGaN Light emitting diodes (LEDs) using polydimethylsiloxane (PDMS) concave microstructures arrays was demonstrated. The size effect of the concave microstructures on the Light Extraction Efficiency of III-Nitride LEDs was studied. Depending on the size of the concave microsturctures, ray tracing simulations show that the use of PDMS concave microstructures arrays can lead to increase in Light Extraction Efficiency of InGaN LEDs by 1.4 to 1.9 times. Experiments utilizing 1.0 μm PDMS concave microstructures arrays demonstrated 1.60 times improvement in Light Extraction, which is consistent with simulated improvement of 1.63 times. The enhancement in Light Extraction Efficiency is attributed to increase in effective photon escape cone due to PDMS concave microstructures arrays, and reduced Fresnel reflection within the photon escape cone due to the grading of refractive index change between GaN / PDMS / air interface.
-
Optimization of Light Extraction Efficiency of III-Nitride LEDs With Self-Assembled Colloidal-Based Microlenses
IEEE Journal of Selected Topics in Quantum Electronics, 2009Co-Authors: Pisist Kumnorkaew, Hongping Zhao, Ronald A Arif, Hua Tong, James F Gilchrist, Nelson TansuAbstract:Improvement of Light Extraction Efficiency of InGaN LEDs using colloidal-based SiO2/polystyrene (PS) microlens arrays was demonstrated. The size effect of the SiO2 microspheres and the thickness effect of the PS layer on the Light Extraction Efficiency of III-nitride LEDs were studied. The monolayer rapid convective deposition conditions for SiO2 microspheres were also investigated. Ray tracing simulations show that the use of microlens arrays can lead to increase in Light Extraction Efficiency of InGaN LEDs by 2.64 times. This is consistent with experiments that demonstrated 2.49 times improvement in Light Extraction utilizing SiO2/PS microlens arrays. The enhancement in Light Extraction Efficiency is attributed to increase in effective photon escape cone due to SiO2/PS microlens arrays, and reduced Fresnel reflection within the photon escape cone due to the grading of refractive index change between GaN/SiO2/PS/air interface.
-
Enhancement of Light Extraction Efficiency of InGaN Quantum Wells LEDs Using SiO 2 Microspheres
2007 Conference on Lasers and Electro-Optics (CLEO), 2007Co-Authors: Pisist Kumnorkaew, Ronald A Arif, James F Gilchrist, Nelson TansuAbstract:Novel approach to improve the Light Extraction Efficiency of InGaN quantum wells Light emitting diodes (LEDs) using SiO2 microspheres was presented, leading to ~232% increase of the LEDs output power.
Seongju Park - One of the best experts on this subject based on the ideXlab platform.
-
Improved Light Extraction Efficiency in Blue Light-Emitting Diodes by SiO2-Coated ZnO Nanorod Arrays
Applied Physics Express, 2013Co-Authors: Chu-young Cho, Na-yeong Kim, Jang-won Kang, Young-chul Leem, Sang-hyun Hong, Wantae Lim, Sung-tae Kim, Seongju ParkAbstract:We report on the improved Light Extraction Efficiency of blue Light-emitting diodes (LEDs) by SiO2-coated ZnO nanorods (NRs) grown on indium–tin oxide (ITO). The optical output power of the LEDs with SiO2-coated ZnO NRs, which are grown on the patterned sapphire substrates, increases by 5% at 20 mA, compared with that of LEDs with bare ZnO NRs. This increase is attributed to the improved Light Extraction Efficiency of LEDs because the SiO2 layer with a refractive index lower than that of ZnO NRs further reduces the Fresnel reflection.
-
improvement of Light Extraction Efficiency of flip chip Light emitting diode by texturing the bottom side surface of sapphire substrate
IEEE Photonics Technology Letters, 2006Co-Authors: Seokin Na, Seongju ParkAbstract:A high Light-Extraction Efficiency was demonstrated in the flip-chip Light-emitting diode (FCLED) with a textured sapphire substrate. The bottom side of a sapphire substrate was patterned using a dry etching process to increase the Light-Extraction Efficiency. Light output power measurements indicated that the scattering of photons emitted in the active layer was considerably enhanced at the textured sapphire substrate resulting in an increase in the probability of escaping from the FCLED. The Light-output power of the FCLED was increased by 40.2% for a 0.4-mum deep FCLED with a periodic distance of 13-mum mesh-type texture on the bottom side of the sapphire substrate
Peng Zhao - One of the best experts on this subject based on the ideXlab platform.
-
Light Extraction Efficiency enhancement for InGaN quantum wells Light-emitting diodes with GaN micro-domes
Light-Emitting Diodes: Materials Devices and Applications for Solid State Lighting XVII, 2013Co-Authors: Peng Zhao, Lu Han, Hongping ZhaoAbstract:The enhancement of Light Extraction Efficiency for thin-film-flip-chip (TFFC) InGaN QWs LEDs with GaN microdomes on n-GaN layer was studied. The three dimensional FDTD method was used to calculate the Light Extraction Efficiency for the TFFC InGaN QWs LEDs emitting at visible spectral regime, as compared to that of the conventional TFFC InGaN QWs LEDs. The calculation indicates significant dependence of the p-GaN layer thickness on the Light Extraction Efficiency. Significant enhancement of the Light Extraction Efficiency (2.5-2.7 times for λpeak=460nm and 2.7- 2.8 times for λpeak=550nm) is achievable from LEDs with GaN micro-domes with optimized micro-dome diameter and height.
-
Analysis of Light Extraction Efficiency Enhancement for Deep Ultraviolet and Visible Light-Emitting Diodes with III-Nitride Micro-Domes
2013Co-Authors: Peng ZhaoAbstract:11 Chapter 1: Introduction 12 1.1 Lighting Energy Consumption and Solid State Lighting for Energy Saving......12 1.2 III-nitride LEDs Introduction 17 1.3 Current Challenges to Pursue High Efficiency III-nitride LEDs 18 1.3.1 Internal Quantum Efficiency Limitation 18 1.3.2 Light Extraction Efficiency Limitation 20 1.4 Recent Approaches to Enhance Light Extraction Efficiency for III-nitride LEDs 21 1.5 Thesis Organization 24 Chapter 2: Finite Difference Time Domain Method for Light Extraction Efficiency Calculation of III-nitride LEDs 26 2.1 Finite Difference Time Domain Method (FDTD) 26 2.1.
-
analysis of tm mode Light Extraction Efficiency enhancement for deep ultraviolet algan quantum wells Light emitting diodes with iii nitride micro domes
Optical Materials Express, 2012Co-Authors: Peng Zhao, Lu Han, Matthew R Mcgoogan, Hongping ZhaoAbstract:Analysis of transverse magnetic (TM) mode Light Extraction Efficiency enhancement for AlGaN quantum wells (QWs) based deep ultraviolet (UV) Light-emitting diodes (LEDs) with III-nitride micro-hemisphere and micro-dome structures on the p-type layer are studied and compared to that of the conventional deep-UV LEDs with flat surface. The transverse electric (TE) and TM components of the spontaneous emission of AlGaN QWs with AlN barriers were calculated by using a self-consistent 6-band k∙p method, which shows the TM component overtakes the TE component and becomes the dominant contribution of the spontaneous emission when the Al-content of the AlGaN QWs is larger than 0.66. The TM mode Light Extraction Efficiency of the deep-UV LEDs emitting at 250 nm with AlGaN micro-domes as compared to the conventional LEDs with flat surface is calculated based on three dimensional finite difference time domain (3D-FDTD) method. The effects of the III-nitride micro-dome diameter and height as well as the p-type layer thickness on the Light Extraction Efficiency were comprehensively studied. The results indicate optimized Light Extraction Efficiency enhancement (>7.3 times) of the dominant TM polarized spontaneous emission for deep-UV LEDs with III-nitride micro-domes.
-
Analysis of Light Extraction Efficiency enhancement for thin-film-flip-chip InGaN quantum wells Light-emitting diodes with GaN micro-domes
Optics Express, 2012Co-Authors: Peng Zhao, Hongping ZhaoAbstract:The enhancement of Light Extraction Efficiency for thin-film flip-chip (TFFC) InGaN quantum wells (QWs) Light-emitting diodes (LEDs) with GaN micro-domes on n-GaN layer was studied. The Light Extraction Efficiency of TFFC InGaN QWs LEDs with GaN micro-domes were calculated and compared to that of the conventional TFFC InGaN QWs LEDs with flat surface. The three dimensional finite difference time domain (3D-FDTD) method was used to calculate the Light Extraction Efficiency for the InGaN QWs LEDs emitting at 460nm and 550 nm, respectively. The effects of the GaN micro-dome feature size and the p-GaN layer thickness on the Light Extraction Efficiency were studied systematically. Studies indicate that the p-GaN layer thickness is critical for optimizing the TFFC LED Light Extraction Efficiency. Significant enhancement of the Light Extraction Efficiency (2.5-2.7 times for λ(peak) = 460nm and 2.7-2.8 times for λ(peak) = 550nm) is achievable from TFFC InGaN QWs LEDs with optimized GaN micro-dome diameter and height.
-
Analysis of Light Extraction Efficiency enhancement for InGaN quantum wells Light-emitting diodes with microspheres
2012 IEEE Energytech, 2012Co-Authors: Peng Zhao, Xuechen Jiao, Hongping ZhaoAbstract:The enhancement of Light Extraction Efficiency for thin-film flip-chip (TFFC) InGaN quantum wells (QWs) Light-emitting diodes (LEDs) with self-assembled microspheres on top of the n-GaN layer was studied. The Light Extraction Efficiency of InGaN QWs LEDs for the three structures with 1) close-packed SiO 2 microlens; 2) close-packed SiO 2 /polystyrene microlens; and 3) GaN micro-hemispheres were calculated and compared to that of the conventional InGaN QWs LEDs with flat surface. Three dimensional finite difference time domain (3D-FDTD) method was used to calculate the Light Extraction Efficiency for TFFC InGaN/GaN QWs LEDs emitting at 460nm. The effects of the microsphere/micro-hemisphere diameter and the p-GaN layer thickness on the Light Extraction Efficiency were studied. Studies show that the p-GaN layer thickness is critical for optimizing the TFFC LED Light Extraction Efficiency. Light Extraction Efficiency enhancement of 1.7 times and 1.85 times were obtained in the TFFC LEDs with SiO 2 microlens and SiO 2 /polystyrene microlens, respectively. More significant enhancement of the Light Extraction Efficiency (>2.6 times) was achieved from LEDs with GaN micro-hemispheres with optimized micro-hemisphere diameter of D=1µm and p-GaN thickness of 195nm.
Ching-fuh Lin - One of the best experts on this subject based on the ideXlab platform.
-
Tunable Light Extraction Efficiency of GaN Light emitting diodes by ZnO nanorod arrays
Semiconductor Science and Technology, 2009Co-Authors: C H Chao, W H Lin, C H Chen, Ching-hua Changjean, Ching-fuh LinAbstract:We report the influence of ZnO nanorod arrays (NRAs) on the Light Extraction Efficiency of GaN Light emitting diodes (LEDs). Our investigation indicates that the output Light intensity of the device exhibits a periodic oscillation as a function of the rod length. The variation of Light Extraction Efficiency is caused by the Fabry–Perot resonance of the film composed of the nanorods. The theoretical analysis shows a good agreement with the measurement results. Our study reveals a method to control the output Light Extraction Efficiency of GaN LEDs via a simple solution-based synthesized ZnO NRAs.