Advantages of the moth‐eye patterned sapphire substrate for the high performance nitride based LEDs
Advantages of the moth‐eye patterned sapphire substrate for the high performance nitride based LEDs
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DOI：
10.1002/pssc.201300492
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
T. Kondo;T. Kitano;Atsushi Suzuki;M. Mori;K. Naniwae;S. Kamiyama;M. Iwaya;T. Takeuchi;I. Akasaki
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文献类型：
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作者：
T. Kondo;T. Kitano;Atsushi Suzuki;M. Mori;K. Naniwae;S. Kamiyama;M. Iwaya;T. Takeuchi;I. Akasaki
我们提出采用蛾眼图案化蓝宝石基板 (MPSS) 作为提高光提取效率并降低 LED 生产成本的解决方案。 MPSS 样品的表面由约 375 nm 高的截锥体组成的三角形网格组成，不同的节距为 460 nm、500 nm、600 nm、700 nm 和 800 nm。实验中还使用市售的图案化蓝宝石基板（PSS）和平面蓝宝石基板（FSS）进行比较。根据阴极发光观察，厚度为 3 µm 的 MPSS 上的 GaN 模板显示出约 1.9 × 108 cm–2 的穿透位错密度（TDD）。透射电子显微镜观察发现，许多位错弯曲并消失，在 MPSS 锥体附近形成环。另一方面，PSS 需要厚度超过 5μm 的 GaN 模板才能达到与 MPSS 相同的 TDD 水平。在所评估的 LED 中，间距为 600 nm 的 MPSS 上的 LED 表现出最高的光输出功率，比 FSS 上的 LED 高 1.89 倍，比 PSS 上的 LED 高 1.05 倍。光输出改善的节距依赖性与 GaN/蓝宝石界面处模拟透射率的节距依赖性一致。经过比较，我们得出结论，MPSS 为高性能 LED 提供了最具成本效益的解决方案。
We propose moth-eye patterned sapphire substrate (MPSS) as a solution to improve the light extraction efficiency and to reduce the production cost of LEDs. The MPSS samples' surfaces consisted of a triangular grid of about 375 nm high truncated cones with different pitches of 460 nm, 500 nm, 600 nm, 700 nm and 800 nm. A commercially available patterned sapphire substrate (PSS) and a flat sapphire substrate (FSS) was also used in the experiments for comparison. According to the cathode luminescence observation, the GaN template on MPSS with a thickness of 3 µm showed a threading dislocation density (TDD) of around 1.9 × 108 cm–2. Transmission electron microscope observation revealed that many of the dislocations were bent and disappeared as loops formed in the vicinity of MPSS cones. On the other hand, PSS required a GaN template thicker than 5µm to achieve a level of TDD equal to MPSS. The LED on MPSS with a pitch of 600 nm showed the highest light output power among the evaluated LEDs as it was 1.89 times higher than that on FSS and 1.05 times higher than that on PSS. The pitch dependence of the light output improvement agrees with the pitch dependence of the simulated transmissivity at the GaN/sapphire interface. As a result of our comparison, we concluded that MPSS provides the most cost effective solution for high performance LEDs.