标题: | 三五族氮化物之成长与应用 Growth and applications of Group III-V nitrides |
作者: | 郭建廷 林建中 程育人 Kuo,Chien-Ting Lin,Chien-Chung Cheng,Yuh -Jen 照明与能源光电博士学位学程 |
关键字: | 氮化铟;氮化镓;图案化蓝宝石基板;紫外光发光二极体;有机金属气相磊晶;光萃取效率;InN;GaN;PSS;Ultraviolet light emitting diode;metal organic chemical vapor deposition;light extraction efficiency |
公开日期: | 2017 |
摘要: | 本篇论文研究了自氮化镓基板的V型凹点的位置点控制了氮化铟的晶体成长。氮化镓晶体利用在蓝宝石基板上之已经圆盘状图案化的二氧化矽侧向成长氮化镓磊晶层来制造V型凹点。其中发现氮化铟晶体择优选在V型凹点的倾斜的{10-11}晶面上生长。一个微米尺度或者更小的V型凹点之尺寸可以在V型凹点底部提供精确的位点控制的氮化为铟原子成核,而在其余的暴露的氮化镓表面上却没有成长氮化铟晶体。而位置点控制的成核作用归因于在V型底部汇聚的六个{10-11}晶面产生的低表面能态点。当铟原子来源供应低于某一数值时,该V型凹点的底部是能够聚集足够的活性源以开始成核反应,从而提供位置点控制晶体成长的唯一位置。 本篇论文研究两种类型之具有空气间隙冠状结构的紫外光发光二极体在典型的氮化铝镓材料透过金属有机化学气相沉积来制作与研究。模拟结果表示,所提出的1.5微米冠状图案化蓝宝石基板制作之紫外发光二极体在中心波长369奈米,可以具有更好的元件性能。将空气间隙之结构导入氮化铝镓发光二极体的概念因而提高光萃取效率的能力已是众所皆知。基本上使用蒙地卡罗方法的光学模拟工具来分析光萃取效率,并且制作实际的光电元件在实验当中进一步验证光线追踪之模拟结果。由蒙地卡罗射光线追踪的模拟结果显示,由于空气间隙的强光反射和重新定向,具有空气间隙的发光二极体结构的光萃取效率将会显着增加。这种高效能的氮化镓发光二极体是由金属有机化学气相沉积机台来制作。在穿透式电子显微镜的影像分析结果显示磊晶侧向成长可以有效抑制晶体线缺陷之过度成长。蒙特卡罗光线追踪模拟结果显示,由于空气间隙的强光反射和重新定向,嵌入空气隙结构的发光二极体之光萃取效率也将显着增加。 本篇论文在图案化蓝宝石基板的微结构几何形状对于氮化镓发光二极体的光萃取效率的影响进行数值分析。研究了各种尺寸的锥形结构以及穹顶和混合式等微结构。发现光萃取效率主要是取决于微结构的表面斜率。光萃取效率随着斜率迅速上升,并且当斜率超过0.6时变平。然而缩小微结构对于光萃取效率则几乎没有影响。与在平坦基板上成长的发光二极体相互比较,发现光线在图案化蓝宝石基板的发光二极体中行进更长的距离。因此保持氮化镓的吸收损耗低对于光萃取效率的优化是重要的。 A site-controlled crystalline InN growth from the V-pits of a GaN substrate was investigated. The V- pits were fabricated by epitaxial lateral growth of GaN over SiO2 disks patterned on a sapphire substrate. InN crystals were found to preferably grow on the inclined {10-11} crystal planes of the V-pits. A V-pit size of 1 μm or less can provide precise site-controlled InN nucleation at the V-pit bottom, while no InN was grown on the rest of the exposed GaN surfaces. The site-controlled nucleation is attributed to the low surface energy point created by the converging six {10-11} crystal facets at the V-pit bottom. When In source supply is below a certain value, this V-pit bottom is the only location able to aggregate enough active sources to start nucleation, thereby providing site-controlled crystal growth. We report two types of crown-shaped with air void in a typical AlGaN-based ultraviolet light-emitting diode (UV-LEDs) with embedded air void array grown by metal–organic chemical vapor deposition are fabricated and investigated. The simulation results demonstrate that the proposed 1.5μm crown-shaped patterned sapphire substrates (CPSS) UV-LEDs (λ~369nm) have better device performances. The concept of introducing air-void structures into AlGaN-based LEDs is well recognized for its ability to enhance the light extraction efficiency (LEE). The LEE analyzed using optical simulation tools based on Monte Carlo method and the ray-tracing simulation results are further validated experimentally by fabricating real devices. The Monte Carlo ray-tracing simulation reveals that the light extraction of the air-voids embedded LED was dramatically increased due to a strong light reflection and redirection by the air voids. The high performance GaN based light-emitting diodes (LEDs) with embedded air void array grown by metal–organic chemical vapor deposition (MOCVD). The transmission electron microscopy images demonstrate that the threading dislocations were significantly suppressed by epitaxial lateral overgrowth (ELOG). The Monte Carlo ray-tracing simulation reveals that the light extraction of the air-voids embedded LED was dramatically increased due to a strong light reflection and redirection by the air voids. The influence of the microstructure geometry of patterned sapphire substrates (PSS) on the light extraction efficiency (LEE) of GaN LED is numerically analyzed. Cone structures of various dimensions are studied, along with dome and mixed microstructures. LEE is found to mainly depend on the microstructure surface slope. LEE rises quickly with slope and flattens out when the slope exceeds 0.6. Scaling down the microstructure has little effect on LEE. Light rays are found to travel longer distances in PSS LEDs, as compared with LEDs grown on a flat substrate. Keeping GaN absorption loss low is important for LEE optimization. |
URI: | http://etd.lib.nctu.edu.tw/cdrfb3/record/nctu/#GT079805804 http://hdl.handle.net/11536/140926 |
显示于类别: | Thesis |