图形蓝宝石衬底GaN基发光二极管的研制

采用抗刻蚀性光刻胶作为掩膜,并利用光刻技术制作周期性结构,进行ICP干法刻蚀C面(0001)蓝宝石制作图形蓝宝石衬底(PSS);然后,在PSS上进行MOCVD制作GaN基发光二极管(LED)外延片;最终,进行芯片制造和测试。PSS的基本结构为圆孔,直径为3μm,间隔为2μm,深度为864 nm,呈六角形分布。与同批生长的普通蓝宝石衬底(CSS)GaN基LED芯片相比,PSS芯片的光强和光通量比CSS分别提高57.32%和28.33%(20 mA),并可减小芯片的反向漏电流,且未影响芯片的波长分布和电压特性。     

GaN外延用蓝宝石衬底的图形化研究进展

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.     

100lm/W照明用LED大功率芯片的产业化研究

本研究基于蓝宝石图形衬底（PSS）制备GaN基40mil功率型LED芯片,结合版图的优化,改善了电流扩展效应,系统研究了LED器件的光电性能。制备的LED外延片波长集中在6nm范围内,半峰宽接近20nm,LED功率型芯片使用优化的版图设计,在0.01mA下有良好的点亮效果,没有暗区,器件在350mA下发光效率达104 lm/W,并能够满足3W的应用市场,此外,器件具有良好的可靠性和稳定性,350mA和700mA下老化1,000hr光衰分别为-0.4%和2.8%,并成功解决了产业化的关键技术。     

LED蓝宝石图形化衬底的研究进展及发展趋势

图形化蓝宝石衬底作为GaN基LED照明外延衬底材料,由于其能降低GaN外延薄膜的线位错密度和提高LED的光萃取效率的显著性能在近几年来引起国内外许多科研机构和厂商的广泛兴趣。从衬底的制备工艺、图形尺寸角度出发,综述了图形化蓝宝石衬底GaN基LED的研究进展,并对其未来在大功率照明市场的应用进行了展望。     

LED用图形化蓝宝石衬底的干法刻蚀工艺

近年来,图形化蓝宝石衬底(PSS)作为GaN基LED外延衬底材料被广泛应用。采用感应耦合等离子体(ICP)技术对涂覆有光刻胶阵列图案的蓝宝石衬底进行刻蚀。通过研究及优化不同ICP刻蚀工艺参数对刻蚀速率和选择比的影响,分别成功制备出蒙古包形和圆锥形图形化蓝宝石衬底片,并在其表面完成InGaN/GaN多量子阱外延及芯片工艺。借助光致发光和电致发光等手段测试其LED器件的光电学性能。实验结果发现圆锥形的图形化蓝宝石衬底拥有更强的光功率和更窄的半峰宽,说明这种形貌的衬底在GaN外延时有效减少了晶格失配造成的缺陷,提高了晶体质量,从而更有效地增加LED出光效率。     

基于Si衬底的功率型GaN基LED制造技术

介绍了Si衬底功率型GaN基LED芯片和封装制造技术,分析了Si衬底功率型GaN基LED芯片制造和封装工艺及关键技术,提供了产品测试数据。Si衬底LED芯片制备采用上下电极垂直结构与Ag反射镜工艺,封装采用仿流明大功率封装,封装后白光LED光通量达80 lm,光效达70 lm/W,产品已达商品化。与蓝宝石和SiC衬底技术路线相比,Si衬底LED芯片具有原创技术产权,可销往任何国家而不受国际专利的限制。产品抗静电性能好,寿命长,可承受的电流密度高,具有单引线垂直结构,器件封装工艺简单,而且生产效率高,成本低廉。其应用前景广阔,是值得大力发展的一门新技术。     

图形化蓝宝石衬底GaN基LED的研究进展

蓝宝石衬底作为发光二极管最常用的衬底,经过不断发展,在克服其与GaN间晶格失配和热膨胀失配问题上,研究人员不断提出解决方案。近期发展起来的图形化衬底技术,除了能减少生长在蓝宝石衬底上GaN之间的差排缺陷,提高磊晶质量以解决失配问题,更能提高LED的出光效率。从衬底图形的形状、尺寸、制备工艺出发,回顾了图形化蓝宝石衬底GaN基LED的研究进展,详细介绍了近年来关于图形化衬底技术与其他技术在提高LED性能方面的结合,总结了图形化蓝宝石衬底应用于大尺寸芯片的优势,并对其未来在大功率照明市场的应用进行了展望。     

六棱锥衬底旋转角影响LED效率的模拟探究

以正六棱锥型图形化蓝宝石衬底GaN基LED为研究对象,设计并探讨了正六棱锥图案在排布过程中旋转角的变化对LED出光效率的影响,得出各面光通量随旋转角变化的规律:在0°～30°范围,随着旋转角的增大,总光通量与顶部光通量有下降趋势,底部光通量有增长趋势。当六棱锥旋转角在0°～6°范围内时,LED芯片的总光通量和顶部光通量均有最优值。综合考虑,旋转角为0°～6°的六棱锥型图形衬底对正装LED的出光效率有最佳的优化效果。     

晶片键合在AlGaInP发光二极管中的应用

(AlxGa1-x)0.5In0.5P高亮度发光二极管是在GaAs衬底上匹配外延的，它的外量子效率受限于吸收光线的GaAs衬底。LED晶片键合技术可以把LED外延片和GaP透明衬底、金属镜面衬底或蓝宝石衬底结合以提高出光效率。本文对上述三种晶片键合的器件制备过程和器件特点进行了描述。     

图形化蓝宝石衬底工艺研究进展

图形化蓝宝石衬底(PSS)技术是一种提高LED亮度的新技术。结合光刻和刻蚀工艺制作图形化蓝宝石衬底。有关图形化蓝宝石衬底的研究主要集中在对光刻和刻蚀工艺的研究,以及图形化蓝宝石衬底提高LED亮度的机理。目前微米级图形化蓝宝石衬底已经得到普遍的应用,与基于平坦蓝宝石衬底的LED相比,PSS-LED的发光功率提高了30%左右。图形化蓝宝石衬底技术的发展经历了从早期的条纹状图形到目前应用较广的半球形和锥形图形,从湿法刻蚀到干法刻蚀,从微米级到纳米级图形的演变。由于能够显著提高LED亮度,纳米级图形化蓝宝石必将得到广泛的运用。     

Investigation of light output performance for gallium nitride-based light-emitting diodes grown on different shapes of patterned sapphire substrate

GaN-based blue light-emitting diodes (LEDs) on various patterned sapphire substrates (PSSs) are investigated in detail. Hemispherical and triangular pyramidal PSSs have been applied to improve the performance of LEDs compared with conventional LEDs grown on planar sapphire substrate. The structural, electrical, and optical properties of these LEDs are investigated. The leakage current is related to the crystalline quality of epitaxial GaN films, and it is improved by using the PSS technique. The light output power and emission efficiency of the LED grown on triangular pyramidal PSS with optimized fill factor show the best performance in all the samples, which indicates that the pattern structure and fill factor of the PSS are related to the capability of light extraction.     

提高基于粉浆法的功率型白光LEDs发光效率的研究

基于水溶性感光胶的自光LEDs平面涂层技术,在蓝光LED芯片表面上得到了可控的荧光粉层．采用降低粉浆中ADC的浓度和提高荧光粉的含量两种措施,减少Cr^3＋在433．6和620nm两处吸收对器件出光效率的影响;新配制的粉浆在暗室中静置3～5h,既可以提高器件的出光效率同时又避免了暗反应带来的影响;在蓝光LED表面上得到粉层后,再涂覆硅胶层,由于硅胶的折射率与粉层的更接近,不但使出光色调偏向蓝光区域而且有更多光子出射,光通量由未加硅胶层时的44．8～59lm提高到了79．4～84．9lm．     

Light output improvement of GaN-based light-emitting diodes grown on Si (111) by a via-thin-film structure

This work reports the fabrication of via-thin-film light-emitting diode (via-TF-LED) to improve the light output power (LOP) of blue/white GaN-based LEDs grown on Si (111) substrates.The as-fabricated via-TF-LEDs were featured with a roughened n-GaN surface and the p-GaN surface bonded to a wafer carrier with a silver-based reflective electrode,together with an array of embedded n-type via pillar metal contact from the p-GaN surface etched through the multiple-quantum-wells (MQWs) into the n-GaN layer.When operated at 350 mA,the via-TF-LED gave an enhanced blue LOP by 7.8％ and over 3.5 times as compared to the vertical thin-film LED (TF-LED) and the conventional lateral structure LED (LS-LED).After covering with yellow phosphor that converts some blue photons into yellow light,the via-TF-LED emitted an enhanced white luminous flux by 13.5％ and over 5 times,as compared with the white TF-LED and the white LS-LED,respectively.The significant LOP improvement of the via-TF-LED was attributed to the elimination of light absorption by the Si (111) epitaxial substrate and the finger-like n-electrodes on the roughened emitting surface.     

白光LED封装用蛾眼化荧光玻璃制备及光学性能

针对荧光玻璃封装白光LED存在的全反射损耗问题,制备了一种蛾眼化荧光玻璃用于提高白光LED光学性能。采用光刻和刻蚀工艺在蓝宝石基片的单面上制作出蛾眼阵列结构,再利用丝网印刷和低温烧结工艺在蓝宝石的另外一面制备YAG∶Ce^3+荧光玻璃层,最后将制备的蛾眼化荧光玻璃用于白光LED封装。通过控制荧光层厚度可以有效调节白光LED发光性能,当荧光层厚度为40μm时,白光LED光效为77.8 lm/W,色温为6024 K,显色指数为69.5。与平面荧光玻璃封装结构相比,在100 mA电流下蛾眼化荧光玻璃封装结构的光效提高了24.9%。结果表明,蛾眼化荧光玻璃提高了白光LED光效,有利于促进荧光玻璃封装白光LED的实际应用。     

荧光粉涂覆方式对白光LED光色指标的影响

文章采用TRACEPRO软件建立了三种白光LED的光学模型:(1)芯片直接涂覆荧光粉;(2)芯片涂覆硅胶后涂覆荧光粉层;(3)芯片涂覆荧光粉后涂覆硅胶层.通过改变荧光粉的摩尔浓度或硅胶厚度来考察白光LED的光色指标,如光通量、色温及显色指数的变化.研究结果表明:第一种和第二种涂覆方式中,光色指标随着荧光粉摩尔浓度或硅胶厚度的改变呈规律性变化;第三种涂覆方式中,色温及显色指数的变化趋势不稳定,第三种方式光通量高于前两种,最大值可达到87.31m.三种方式的显色指数在70左右.研究结论为白光LED工艺设计提供参考和依据.     

Enhancement of light extraction efficiency of GaN-based light-emitting diode using ZnO sol-gel direct imprinting

ZnO nano-structures were formed on transparent conducting oxide layer of GaN LED device on non-patterned (non-PSS) and patterned sapphire substrates (PSS). Since ZnO nano-structures were formed by sol-gel direct imprinting process, plasma etching process, which may create the plasma induced damage, was not used. Due to the ZnO nano-structures, light extracted from active layer was coupled with ZnO nano-structures and thus total internal reflection at the ITO layer was suppressed. According to electroluminescence measurement, the emission intensities of GaN LED devices with ZnO nano-structures, on both non-PSS and PSS sapphire substrates were increased by 20.5% and 19.0%, respectively, compared to GaN LED devices without ZnO nano-structures, due to the suppression of total internal reflection. Moreover, it is confirmed that there is no decrease of light extraction on side direction due to light focusing to vertical axis by nanostructure. Electrical performance of GaN LED devices were not degraded by ZnO sol-gel direct imprinting process.