共查询到18条相似文献,搜索用时 46 毫秒
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基于时域有限差分法(FDTD)在GaN基LED表面分别生长了 ZnO柱状与锥状微纳结构,并利用Rsoft模拟仿真软件分析了两种结构的几何参量(排列周期p、高度H、底面直径D等)对GaN基LED光提取效率的影响.结果表明两种结构均可提高器件的光提取效率,柱状结构在H=0.25 μm,p=1.5 μm,D=0.9μm时表现最优,其光提取效率是未加任何结构平板LED的5.6倍;而锥状结构在H=0.6μm,p=1.4 μm,D=1.4 μm时表现最优,其光提取效率是未加任何结构平板LED的5.3倍.研究结果对高性能GaN基LED的设计与制备具有一定指导意义. 相似文献
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因蓝宝石具有良好的稳定性能,且其生产技术成熟,是目前异质外延GaN应用最广泛的衬底材料之一.采用图形化蓝宝石衬底技术可以降低GaN外延层材料的位错密度,提高LED的内量子效率,同时提高LED出光效率提高,近年来引起了国内外的广泛关注.概述了图形化蓝宝石衬底的研究进展,包括图形化蓝宝石衬底的制备工艺、图形尺寸、图形形状及图形化蓝宝石衬底的作用机理;详细介绍了凹槽状、圆孔状、圆锥形、梯形和半球状5种图形形状,并分析了GaN材料在不同图形形状的图形化蓝宝石衬底上的生长机理及不同图形形状对GaN基LED器件性能的影响.对图形化蓝宝石衬底技术的研究方向进行了展望,提出了亟待研究和解决的问题. 相似文献
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为了提升垂直结构LED提取效率,针对器件侧壁出光的研究越发引起研究人员的关注。由于GaN的高折射率,大部分有源区发出的光线将被限制在GaN层内横向传输。对不同刻蚀倾角侧面的光提取效率进行分析模拟,模拟结果显示,LED的提取效率可以通过侧壁倾斜角度的优化得以提升。实验结果表明,特定侧壁倾角器件的提取效率相比较垂直侧壁提高了18.75%,电致发光光谱测试(EL)结果表明,实验结论与理论计算值基本吻合。本结论对垂直结构GaN基LED器件的优化设计与性能提升有重要指导意义。 相似文献
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实验研究了恒流驱动条件下,GaN基白光LED的正向电压、发光光谱和发光效率随环境温度的变化情况.结果表明,在输入电流恒定的情况下,随着温度的升高,结电压和发光强度与温度具有良好的线性关系,并且GaN基白光LED的发光颜色总是向蓝光漂移,而小电流驱动时比大电流驱动时蓝光漂移更明显.根据实验结果,分析了器件的最佳额定工作电流.Abstract: Under a constant driving current, the changes of the forward voltage, emission spectrum and luminous efficiency of GaN-based White LEDs with the ambient temperature are studied experimentally. It is found that the forward voltage and the luminous intensity depend on the temperature linearly with constant injection current, and luminous colors of GaN-based White LEDs always shift towards blue. And the blue shift with low driving current is more obvious than that with high driving current. According to the results, the best rated operating current of GaN-based white LEDs is discussed. 相似文献
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首先分析了在制作GaN基LED时,采用干法刻蚀技术会对材料的表面和量子阱有源区造成损伤,影响了GaN基LED的内量子效率。针对这个问题,研究实验采用感应耦合等离子反应刻蚀(ICP-RIE)技术,分别选择了氯气/三氯化硼(Cl2/BCl3)气体体系和氯气/氩气(Cl2/Ar)气体体系,通过优化射频功率、ICP功率、气体流量以及相应的真空度,得到了良好的刻蚀端面,对于材料造成的损伤较低,得到更好的I-V特性。实验结果表明,采用低损伤的偏压功率刻蚀后制作的LED器件,出光功率提升一倍以上,同时采用Cl2/Ar气体体系,改善了器件的I-V特性,有效提高了LED的出光效率。 相似文献
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《Photonics Technology Letters, IEEE》2009,21(12):760-762
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Ja-Yeon Kim Min-Ki Kwon Jae-Pil Kim Seong-Ju Park 《Photonics Technology Letters, IEEE》2007,19(23):1865-1867
This study investigated the characteristics of a triangular light-emitting diode (LED) and compared it to a standard quadrangular LED. The total radiant flux from the packaged triangular LED increased by 48% and 24% at input currents of 20 and 100 mA, respectively, compared to that of a quadrangular LED which was grown on patterned sapphire substrate. In light far-field beam distribution, the light extraction in the horizontal direction of the LED was much higher than that of the quadrangular LED due to the enhancement of light emission from the side walls of the triangular LED. 相似文献
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Kui Bao Xiang Ning Kang Bei Zhang Tao Dai Chang Xiong Hang Ji Guo Yi Zhang Yong Chen 《Photonics Technology Letters, IEEE》2007,19(22):1840-1842
To improve surface light extraction of GaN-based flip-chip light-emitting diodes (FC-LEDs), we employed an imprint approach of thermosetting polymer for patterning microscale surface grating on the polymer encapsulant. One-dimensional (1-D) and two-dimensional (2-D) taper-like polymer gratings with a period of 6 mum were successfully realized on encapsulant above the sapphire backplane of GaN LED. By adopting the 1-D and 2-D taper-like grating encapsulant, the improvement of light extraction from the 1 mm times 1 mm FC-blue LED with a reflective Ag film on the p-side was about 18.5% and 31.9% compared to the LED encapsulated by flat polymer, respectively. To evaluate the concept of a diffraction grating in enhancement of light extraction, we performed a simulation of diffraction based on 1-D rigorous coupled wave analysis with the supporting experiments. 相似文献
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《Electron Device Letters, IEEE》2009,30(5):496-498
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High Brightness GaN-Based Light-Emitting Diodes 总被引:1,自引:0,他引:1
Ya-Ju Lee Tien-Chang Lu Hao-Chung Kuo Shing-Chung Wang 《Display Technology, Journal of》2007,3(2):118-125
This paper reviews our recent progress of GaN-based high brightness light-emitting diodes (LEDs). Firstly, by adopting chemical wet etching patterned sapphire substrates in GaN-based LEDs, not only could increase the extraction quantum efficiency, but also improve the internal quantum efficiency. Secondly, we present a high light-extraction 465-nm GaN-based vertical light-emitting diode structure with double diffuse surfaces. The external quantum efficiency was demonstrated to be about 40%. The high performance LED was achieved mainly due to the strong guided-light scattering efficiency while employing double diffuse surfaces 相似文献
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Tien-Chang Lu Tsung-Ting Kao Chih-Chiang Kao Jung-Tang Chu Kang-Fan Yeh Li-Fan Lin Yu-Chun Peng Hung-Wen Huang Hao-Chung Kuo Shing-Chung Wang 《Electron Device Letters, IEEE》2007,28(10):884-886
We report a fabrication and demonstration of a GaN-based high-Q vertical-cavity light-emitting diode (VCLED). The GaN VCLED is composed of a 25-pair high-reflectivity (98%) GaN/AlN distributed Bragg reflector (DBR), an eight-pair SiO2/Ta2O5 dielectric DBR (99%), and a three-lambda optical thickness InGaN/GaN active region. It shows a very narrow linewidth of 0.52 nm, corresponding to a cavity Q -value of 895 at a driving current of 10 mA and a dominant emission peak wavelength at 465.3 nm. In addition, this VCLED emission linewidth continues to decrease with an increasing injection current, suggesting a possible realization of GaN-based vertical-cavity surface emitting lasers. 相似文献
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Shi J.-W. Sheu J.-K. Wang C.-K. Chen C.-C. Hsieh C.-H. Chyi J.-I. Lai W.-C. 《Photonics Technology Letters, IEEE》2007,19(18):1368-1370
In the following study, we demonstrated linear cascade GaN-based light-emitting-diode (LED) arrays at a wavelength of approximately 520 nm. Experimental LEDs were analyzed with the goal to improve the output power and differential efficiency of a single LED. The study shows that using arrays with up to four LEDs connected in series, we can achieve four times the improvement in output power (differential quantum efficiency) under the same bias current as compared to a single LED apparatus. We have also measured the modulation-speed performance of experimental LEDs, and both devices exhibit similar 3-dB bandwidth (90 MHz) under the same bias currents. Experimental results indicate that the cascade connection offers the advantages of significantly enhanced external differential efficiency and provision of a method to use a constant-voltage power supply. The current crowding problem and resistance-capacitance-limited bandwidth degradation issues in a large active area LED can also be minimized using the connection demonstrated in our experiment. 相似文献
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Two foundational factors (escape cone and transmissivity) about light extraction of light emitting diodes (LEDs) are discussed.According to these factors,a new process to simulate the light extraction of LEDs based on the Monte Carlo method has been provided.The improved method is to deal with the reflection and refraction of light (beam of light) at the interface between two mediums approximately.In addition,light extraction of traditional LEDs is simulated by different processes with the same structure and parameters.The results show that the reflection and refraction of light processed approximately are accurate enough for analyzing LEDs structure.This method saves much time and improves efficiency in the simulation of light extraction of LEDs. 相似文献