利用纳米压印技术制备光子晶体LED地研究.pdf

华中科技大学硕士学位论文 I 摘要因为具有高效率、可靠性、低功耗和稳定性的优点,发光二极管( LED )作为新一代的照明光源获得了快速发展。但是由于 GaN 的高折射率( n= )导致光从 GaN 中逸出的临界角大约为 24 度, LED 的光提取效率仅仅只有 4% 。光子晶体作为一种有效的提高 LED 光萃取效率的方法,近十年来受到了广泛的研究。本论文主要对蓝光波段光子晶体的设计和纳米压印制备光子晶体 LED 进行研究。采用 Rsoft 软件对四种常见光子晶体结构进行了模拟设计, 并结合制备工艺和 ITO 扩展电极的导电效应进行分析比较,最终选择三角空气孔阵列光子晶体结构,光子晶体优化参数为占空比 Rp= 、周期 a=418nm 、半径 r=167nm 。实验采用纳米压印技术和 ICP (感应耦合等离子体)刻蚀技术在蓝光 LED 的 P-GaN 层上制备光子晶体。为了减少工艺对 LED 的损伤,我们对纳米压印技术和 ICP 刻蚀技术参数进行了改进,采用二次纳米压印,软压印和低 RF 功率 ICP 刻蚀的方法制备光子晶体图案。实验结果显示光子晶体图案成功转移到 P 型层上,直径大约 312nm ,周期大约 410nm ,误差小于 7% 。光子晶体刻蚀深度为 70nm 的 LED 外延片对比没有图形的 LED 外延片光致发光强度提高 2 倍。在 350mA 电流注入条件下, 刻蚀深度为 70nm 和 100nm 的光子晶体 LED 芯片对比没有图形的 LED 芯片光功率分别提高 10% 和 7% ,光子晶体 LED 相对无图形 LED 的正向电压变化不大。关键词: 发光二极管纳米压印光子晶体华中科技大学硕士学位论文 II Abstract The light emitting diodes(LED) has flourished for the past few decades as ultimate light source. High efficiency, reliability, low power consumption and durability are the key factors for the rapid development of the LED. There is only 4% of the internal light would be extracted from surface, because the high refractiv e index of GaN results in a critical angle foe the light escape cone to be about 24 o. This thesis focus on the research of de sign of photonic crystal and fabrication of Photonic crystal LED. We design four lattice arra ys of photonic crystal by Rsoft, and analyze the design with fabrication t echnology and conductive effect of ITO electrode. Triangular lattice 2D photonic crystal with air hole is c hoosed for fabrication. The duty cycle, period and radius of photonic crystal are , 418nm, 1 67nm, respectively. Th e photonic crystal is made on P-GaN layer of blue LED by na noimprint lithography and ICP etching. For reducing the damage of LED, we employ twice nanoimprint, soft impr int and ICP etching with low RF power for fabrication of photonic crystal. The result of experiment s hows that the photoni c crystal was essf ul transferred to P-GaN layer. After laser pump, the intensity of the PL(photolu