标题: | 改善电洞传导行为缓解Ⅲ族氮化物发光二极体效率下降特性之研究 Efficiency droop alleviation in Ⅲ-nitride light-emitting diodes by improving hole transportation |
作者: | 张玮婷 Chang, Wei-Ting 林烜辉 郭浩中 Lin, Shiuan-Huei Kuo, Hao-Chung 电子物理系所 |
关键字: | 发光二极体;量子效率;light-emitting diodes;LED;efficiency droop |
公开日期: | 2010 |
摘要: | 本论文中,我们针对为传统氮化铟镓发光二极体的磊晶结构进行改良,改善电洞传导行为以缓解三族氮化物发光二极体效率随外加电流提高而骤降之问题。 第一部分设计渐变铝含量的氮化铝镓电子阻挡层,期待除了强化阻档电子溢流外,更可增加电洞注入效率,藉以提升主动层载子复合发光效率,在以理论分析找得最佳化设计后,实作样品利用电激发萤光(Electroluminescence, EL)量测,验证其发光强度确实相较于使用传统电子阻挡层之元件为佳,并且缓解了发光效率在高电流会产生效率骤降的情况。 再者,我们在使用氮化铟镓作为主动层量子井的紫外光(UV) LED中,将位能障材料氮化铝镓替换成氮化铝镓铟,量测证实其与三元材料晶格常数和能隙相近的四元材料,有较好的磊晶品质外,EL量测结果也显示其突出的电特性与发光效率。由于四元材料可以经由调整铝和铟的含量而自由变动其晶格常数、能隙、应力、和载子局限效果,因此在藉由理论模拟分析后,我们推论使用氮化铝镓铟作为位能障,可以提高量子井中电子的局限、电洞的传导与载子的迁移率,因而改善LED效率骤降的问题。 In this thesis, we designed the epitaxial structure of InGaN light-emitting diodes (LEDs) to improve the transportation of holes, which leads to reduction of efficiency droop. We first degined a graded-composition electron blocking layer (GEBL) for c-plane InGaN/GaN LEDs. The simulation results demonstrated that such GEBL can effectively enhance the capability of hole transportation across the EBL as well as the electron confinement. Consequently, the LED with GEBL grown by metal-organic chemical vapor deposition exhibited lower forward voltage and series resistance, and much higher output power at high current density, as compared to conventional LED. Second, we demonstrated InGaN-based UV LEDs with AlGaN and InAlGaN barrier. EL results indicate that the light output performance could be enhanced effectively when replacing the conventional AlGaN barriers by InAlGaN barriers. Furthermore, from numerical analysis, it is believed that InGaN/AlInGaN MQWs exhibit higher radiative recombination rate and low efficiency droop at a high injection current because of the better band-offset ratio and the higher hole mobility, which leads to the uniform distribution of holes in the active region. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079821519 http://hdl.handle.net/11536/47449 |
显示于类别: | Thesis |
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