SIMS2015 Session MI-TuP: Microelectronics Poster Session
Tuesday, September 15, 2015 5:20 PM in Grand Ballroom III
Tuesday Afternoon
Time Period TuP Sessions | Topic MI Sessions | Time Periods | Topics | SIMS2015 Schedule
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MI-TuP-1 The Failure Analysis of Middle-power GaN-based Light-emitting Diodes with Green and Red Phosphors using TOF-SIMS
Haicheng Cao, JiaJia Fu, Xuejiao Sun, Baojuan Sun (Chinese Academy of Sciences, Beijing, P. R. China); Zhanping Li (Tsinghua University, Beijing, P. R. China); Lixia Zhao (Chinese Academy of Sciences, Beijing, P. R. China) GaN-based LEDs coated with phosphors have developed significantly and have already been used in many kinds of application, such as solid-state lightings and displays. However, the reliability issue is still a remaining challenge to restrict the further development. In addition, except for the yellow phosphors, green and red phosphors have also been used in order to improve the light quality. In this study, mid-power GaN-based LEDs samples with green/red mixed phosphors (GR) were prepared, which were packaged with silicone/phosphors mixtures encapsulation in the same structure at the same time. The chemical components of red and green phosphors are Sr0.9Ca0.1AlSiN3: Eu2+ and SrSi2O2N2: Eu2+, respectively. After the highly accelerated life test at 85oC for ~560 hours, the light output decreased by 30% and there is an obvious brown color appearing in the silicone and phosphor area. LEDs with green phosphor degraded much faster than red ones. While using I-V characteristics, there is no difference after the degradation. The reflection spectroscopy also showed a decrease of the refractive index for silicone encapsulation. In order to further understand the change in the structure, we use Time of Flight-Secondary Ion Mass Spectrometry (TOF-SIMS) to compare the chemical information in the silicone and phosphor mixtures before and after degradation. The mass spectroscopy shows that after degradation, amounts of (Ca,Sr)OH+, CaNOH2+ and (Ca,Sr)2OH+ were produced, indicating a reaction may occur between phosphor and silicone at the high temperature during the operation, which may lead to the decrease of the encapsulation transparency and discoloration of the encapsulation. This result is also consistent with the SEM. This study provide a direct evidence for the failure mechanism of the GaN-based LEDs using TOF-SIMS, which will be helpful to further improve and predict the reliability of this kind of devices. word: Phosphors, Failure Analysis, GaN-based LEDs, TOF-SIMS |