Nanoheteroepitaxy of (In,Ga)N: Toward a Phosphor-Free White LED

(In,Ga)N 纳米异质外延：迈向无磷白光 LED

• 批准号: 0424161
• 负责人: Timothy Sands
• 金额: $ 21万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-15 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0424161&HistoricalAwards=false
• 关键词: Nanoheteroepitaxy; Ga; Toward; Phosphor; Free

0424161SANDSGoal: The proposed research is directed toward the goal of demonstrating bright red (~650 nm) electroluminescence from an (In,Ga,Al)N light-emitting diode (LED) employing an active region consisting of an array of dislocation-free strained (In,Ga)N nanorod heterostructures. Significance: National and international solid-state lighting initiatives are aimed at replacing fluorescent and incandescent lighting technologies with an LED alternative. A white LED replacement technology with luminous efficiency of 200 lm/W, color temperature comparable to the midday sun, and color rendering equivalent to conventional illumination sources has the potential to reduce overall electric power consumption and the associated power-plant emissions by 10%. Combining discrete red (In,Ga,Al)P LEDs with green and blue (In,Ga,Al)N LEDs may suffice for large outdoor displays, but this approach is too costly for general white-light illumination. Today's most promising approaches utilize down-conversion of blue or UV LED light with phosphors. However, efficiency and lifetime limitations inherent to phosphor-based white LEDs suggest that a phosphor-free alternative will be required. Approach: The phosphors could be eliminated if one materials system could be utilized for emission across the entire visible spectrum. Conventional planar (In,Ga,Al)N LED heterostructures can be designed to emit from the UV into the yellow. However, the large lattice mismatch between InN and GaN (10.8%) prevents the fabrication of bright orange and red LEDs. The proposed research program is based on the concept that lateral elastic strain relief in the nanorod topology can extend the range of lattice-mismatch that can be accommodated coherently in an (In,Ga)N heterostructure, thereby enabling the fabrication of bright (In,Ga,Al)N LEDs across the entire visible spectrum. Self-organized GaN and (In,Ga)N nanorods have been grown by halide vapor phase epitaxy (HVPE) and rf-plasma molecular beam epitaxy without the use of foreign metal catalysts, suggesting that the nanorod approach to a red LED may be feasible. The proposed research will fund the P.I. and two of his graduate students (one fully dedicated to this project, and a second who will split his or her effort with another project that requires the same skill set) to identify the factors that control the nanorod growth regimes in HVPE, metalorganic chemical vapor deposition and reactive pulsed laser deposition (PLD). The theories of nanoheteroepitaxy will be tested, and methods to control the nanorod diameter distribution using porous anodic alumina templates will be explored. The work will culminate in an attempt to demonstrate an (In,Ga)N nanorod-array LED with a peak emission wavelength of ~650 nm (red). The P.I. and his students have unique facilities to pursue this research, including a custom HVPE reactor for (In,Ga)N nanorod synthesis, and a load-locked PLD system with ammonia process gas and group-III metal targets.Broader ImpactsInterdisciplinary Research Environment: The proposed research program will support graduate student research in an interdisciplinary environment. The P.I. has a joint appointment in ECE and MSE at Purdue, and his research group is evenly populated with MSE and ECE graduate and undergraduate students, all of whom are actively involved in the Birck Nanotechnology Center. Outreach: The P.I. proposes to complement the proposed research program with the development of a 30-min hands-on presentation than can be tuned for elementary, secondary and adult layperson audiences. The focus of the presentation will be on LEDs as an emerging nanotechnology success story, taking advantage of the sensory stimulation and curiosity naturally evoked by these bright light sources. The presentation will also bring in elements of other energy conversion technologies that might benefit from nanotechnology, including solid-state cooling, and the potential impacts of these new technologies on society. Senior Design Projects: The P.I. will invoke the scientific and technological contexts of the proposed research program in an annual MSE Senior Project, involving 4-6 undergraduate students each academic year. The students will utilize the laboratory facilities and interact with industrial mentors in the design of novel growth, etching and nanofabrication processes for III-V nitride heterostructures.

0424161 SANDS目标：提出的研究是针对的目标，展示明亮的红色（~650 nm）电致发光从（In，Ga，Al）N发光二极管（LED）采用的有源区组成的一个阵列的无位错应变（In，Ga）N纳米棒异质结。 重要性：国家和国际固态照明计划旨在用LED替代品取代荧光灯和白炽灯照明技术。 一种白色LED替代技术，其发光效率为200 lm/W，色温与正午太阳相当，显色性与传统照明光源相当，有可能将总电力消耗和相关的发电厂排放减少10%。 将分立的红色（In，Ga，Al）P LED与绿色和蓝色（In，Ga，Al）N LED组合可以满足大型户外显示器，但是这种方法对于一般的白光照明来说成本太高。 当今最有前途的方法利用具有磷光体的蓝色或UV LED光的下转换。然而，基于磷光体的白色LED固有的效率和寿命限制表明将需要无磷光体的替代品。方法：如果一种材料系统可以用于整个可见光谱的发射，则可以消除磷光体。 传统的平面（In，Ga，Al）N LED异质结构可以被设计成从UV发射到黄色。 然而，InN和GaN之间的大晶格失配（10.8%）阻止了明亮的橙子和红色LED的制造。 所提出的研究计划是基于这样的概念，即纳米棒拓扑结构中的横向弹性应变消除可以扩展可以在（In，Ga）N异质结构中相干地容纳的晶格失配的范围，从而能够在整个可见光谱中制造明亮的（In，Ga，Al）N LED。 自组织GaN和（In，Ga）N纳米棒已经通过卤化物气相外延（HVPE）和射频等离子体分子束外延生长，而不使用外来金属催化剂，这表明纳米棒的红色LED的方法可能是可行的。拟议的研究将资助P.I.和他的两个研究生（一个完全致力于这个项目，第二个谁将他或她的努力与另一个项目，需要相同的技能集），以确定控制HVPE，金属有机化学气相沉积和反应脉冲激光沉积（PLD）的纳米棒生长制度的因素。 本研究将测试奈米异质磊晶理论，并探讨利用多孔阳极氧化铝模板控制奈米棒直径分布的方法。 这项工作的最终目的是尝试展示峰值发射波长约为650 nm（红色）的（In，Ga）N纳米棒阵列LED。 私家侦探他和他的学生有独特的设施来进行这项研究，包括定制HVPE反应器（In，Ga）N纳米棒合成，和负载锁定PLD系统与氨工艺气体和第三族金属targes.Broader ImpactsInterdisciplinary研究环境：拟议的研究计划将支持研究生在跨学科的环境中的研究。 私家侦探在普渡大学的ECE和MSE联合任命，他的研究小组与MSE和ECE研究生和本科生，所有这些人都积极参与伯克纳米技术中心均匀填充。外展：PI建议补充拟议的研究计划，开发一个30分钟的动手演示比可以调整为小学，中学和成人外行观众。 演讲的重点将是LED作为一个新兴的纳米技术的成功故事，利用这些明亮的光源自然引起的感官刺激和好奇心。 该演讲还将介绍可能受益于纳米技术的其他能源转换技术的元素，包括固态冷却，以及这些新技术对社会的潜在影响。高级设计项目：P.I.将在每年的MSE高级项目中调用拟议研究计划的科学和技术背景，每个学年涉及4-6名本科生。 学生将利用实验室设施，并在III-V氮化物异质结构的新型生长，蚀刻和纳米加工工艺的设计与工业导师互动。