GaN基蓝光LED内量子效率的温度droop效应研究

GaN-based LED suffer from a strong decrease in internal quantum efficiency with increasing temperature, which is called the temperature droop. The temperature droop can be more detrimental than the current-density droop that means the efficiency decrease with increasing operating current. It is very helpful for improving LED efficiency and application to eliminate the temperature droop. Until now, however, the temperature droop has been less focused on, and the causes of the temperature droop is not comprehensive. The project will be based on the technology of GaN-based LED on Si substrate. Mechanisms that are related to internal quantum efficency will be researched, and their variations with temperature will be understood by combinating theory and experiment. The effect of mechanisms on the temperature droop will be quantificationally analysed by the combination of analytical method and numerical method. The causes of the temperature droop will be comprehended from theory models, which can give a guidance to the experiment. Conversely, theory models can be validated and constantly revised by analysing experiment results. The scheme of improving temperature droop will be proposed, and LED chip with high internal quantum efficiency will be designed and fabricated.

随工作环境温度的升高，GaN基LED的内量子效率显著下降；该现象被称为温度droop效应。温度droop效应对发光效率的影响甚至会超过随电流密度增加而产生的droop效应。如能消除温度droop效应问题，将可大幅提高GaN基LED在正常工作温度下的发光效率，拓展其应用领域。然而，目前很少有文献报道对温度droop效应的研究，对于其背后的深层物理机理还未有清晰的认识。本项目将以本单位自主研发的硅衬底GaN基LED技术为平台，采用理论与实验相结合的方式系统研究各相关物理机制随温度变化时对内量子效率的影响趋势；并使用解释方法与数值方法相结合进行定量分析。从理论中深入理解T-droop效应产生的原因后，给实验以指导；反过来，又用实验对理论进行验证并不断修正理论模型；进而提出解决温度droop效应问题的方案，设计并制造出更高效的GaN基LED芯片。

随工作环境温度的升高，GaN基LED的内量子效率显著下降；该现象被称为温度droop效应。温度droop效应对发光效率的影响甚至会超过随电流密度增加而产生的droop效应。然而，我们对温度droop效应背后的深层物理机理还所知甚少。本项目正是在此背景下立项的，旨在探索温度droop效应背后的物理机制，理解T-droop效应产生的原因。在项目执行的过程中，我们取得如下的研究成果： （1）完成了LED器件模拟的建模工作；创造性地在模拟模型中引入V坑模型，研究了V坑的作用机理。（2）采用实验与理论模拟相结合的方法，研究了V坑大小及密度对LED光电性能的影响，结果认为：位错密度并不是越小越好，而是存在一最佳值。（3）实验与理论结合，研究了各种LED芯片的变温特性，探索影响LED温度droop性能的物理机制；包括V坑、应力、掺杂以及量子阱结构等都对温度droop有较大影响，并发现电子泄露是引起温度droop的重要原因。这些研究成果揭示了InGaN/GaN多量子阱LED的重要物理机理。本项目部分成果已应用于硅衬底GaN基蓝、绿LED的产业化，在改善产品的耐高温性能、提升LED光电性能作出了贡献。