基于高反射率DBR薄膜的倒装LED电极结构优化设计  

Optimization of Electrode Structure for Flip-chip LED Based on DBR Reflector

作　　者：吕家将[1] 刘星童 LV Jiajiang;LIU Xingtong(School of Mechanical Engin.,Jiujiang Vocational and Technical College,Jiujiang 332007,CHN;School of Power and Mechanical Engin.,Wuhan University,Wuhan 430072,CHN)

机构地区：[1]九江职业技术学院机械工程学院,江西九江332007 [2]武汉大学动力与机械学院,武汉430072

出　　处：《半导体光电》2019年第6期776-780,共5页Semiconductor Optoelectronics

基　　金：江西省教育厅科学技术研究项目(GJJ171249)

摘　　要：为提升LED芯片的光提取效率和电流扩展能力,设计了双金属层环形叉指结构ITO/DBR电极的大功率倒装LED芯片,并对分布式布拉格反射镜(DBR)薄膜和环形叉指电极结构进行了仿真优化计算。利用TFcalc软件仿真计算了DBR堆栈方式、堆栈周期和参考波长对DBR反射率的影响。仿真结果表明,优化设计的双堆栈DBR薄膜在234nm宽波长范围内反射率均高于95%,对应蓝黄光区域(440~610nm)平均反射率高达98.95%,参考波长红移可以缓解DBR反射偏振效应。利用SimuLED软件仿真计算了电极结构对芯片电流扩展能力的影响。仿真结果表明,350mA电流输入情况下,单金属层电极电流密度均方差为44.36A/cm^2,而双金属层环形叉指数目为3×3时,电流密度均方差降至14.37A/cm^2。双金属层环形叉指电极降低了p、n电极间距,减小了电流流动路径,芯片电流扩展性能明显提升。To improve the light extraction efficiency and current spreading characteristic of LED chips,a novel kind of high power flip-chip LEDs with annular finger-like two-level metallization ITO/DBR electrode was presented,and the distributed Bragg reflectors(DBR)film and geometric topology of the electrodes were optimized by simulations.The influence of DBR stack mode,stack period and reference wavelength on DBR reflectivity was simulated with TFcalc software.The results show the reflectance of optimized DBR is higher than 95% over234 nm wavelength bandwidth,and the average reflectivity is higher than 98.95% in the wavelength range of 440~610 nm.The influence of electrodes geometric topology on current spreading characteristic was also studied by SimuLED.The results show the standard deviation of current density is decreased from 44.36 to 14.37 A/cm^2 at 350 mA for the high power flip-chip LEDs with 3×3 annular finger-like two-level metallization electrode.Annular finger-like twolevel metallization electrode for flip-chip LEDs reduces the space between p and n electrodes,and shortens the current flow path,leading to a more favorable uniformity of current spreading.

关 键 词：倒装LED 分布式布拉格反射镜 双金属层电极 环形叉指 平均反射率 

分 类 号：TN312.8[电子电信—物理电子学]