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4 January 2008 Design and optimization of dielectric optical coatings for GaN based high bright LEDs
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Abstract
Different types of dielectric optical coatings for GaN based high bright LEDs were designed and discussed. The optical coatings included the anti-reflection (AR) coating, high-reflection (HR) coating, and omni-directional high reflection coating. Main materials for the optical coatings were dielectric materials such as SiO2, Ta2O5 and Al2O3, which were different from the metallic reflector such as Ag usually used now. For the application of anti-reflection coating in GaN LEDs, it was introduced into the design of transparent electrodes with transparent materials such as ITO to form combined transparent electrodes. With the design of P, N transparent electrodes using the AR coating and ITO for GaN LEDs, the extraction efficiency was improved by about 15% experimentally. For the dielectric high-reflection coating, it has higher reflectivity and lower absorption than the metal reflector, and it was supposed to improve the extraction efficiency obviously. While the dielectric omni-directional reflection coating using dielectric materials was also designed and discussed in this article, since which was anticipated to improve the extraction efficiency furthermore. Using SiO2 and Ta2O5, the average reflectivity of a design of all dielectric omni-directional high reflection coating on the sapphire surface was over 94%.
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Xiaodong Wang, Yan Li, Hua Yang, Xiaoyan Yi, Liangchen Wang, Guohong Wang, Fuhua Yang, and Jinmin Li "Design and optimization of dielectric optical coatings for GaN based high bright LEDs", Proc. SPIE 6841, Solid State Lighting and Solar Energy Technologies, 68410E (4 January 2008); https://doi.org/10.1117/12.765228
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