We conducted a systematic investigation of the light extraction efficiency (LEE) of GaN-based vertical micro-scale light-emitting diode (μ-LED) structures using three-dimensional finite-difference time-domain (FDTD) simulations. The LEE of μ-LED structures was found to have a strong dependence on structural parameters such as the shape of the chip cross section, chip dimension, and p-GaN thickness. The LEE of a μ-LED with a circular cross section was lower than that of a μ-LED with a square cross section by 5∼10% owing to the coupling of light with high-quality-factor whispering gallery modes. The LEE of a μ-LED structure decreased as the chip dimension increased, which could be attributed to the increased portion of trapped light inside the LED chip and increased light absorption in the GaN with an increasing chip dimension. In addition, the LEE varied significantly with the thickness of the p-GaN layer, which could be explained by the strong dependence of the angular distribution of the emission pattern on the p-GaN thickness. The FDTD simulation method presented in this study is expected to be advantageously employed in designing μ-LED structures with high LEE.

中文翻译：

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使用有限差分时域仿真研究基于 GaN 的微型发光二极管的光提取效率

我们使用三维有限差分时域 (FDTD) 模拟对基于 GaN 的垂直微尺度发光二极管 (μ-LED) 结构的光提取效率 (LEE) 进行了系统研究。发现 μ-LED 结构的 LEE 对结构参数有很强的依赖性，例如芯片横截面的形状、芯片尺寸和 p-GaN 厚度。由于光与高品质因子回音壁模式的耦合，圆形截面的 μ-LED 的 LEE 比方形截面的 μ-LED 低 5%~10%。μ-LED 结构的 LEE 随着芯片尺寸的增加而降低，这可能是由于 LED 芯片内部被困光的部分增加，并且随着芯片尺寸的增加，GaN 中的光吸收增加。此外，LEE 随 p-GaN 层的厚度而显着变化，这可以通过发射图案的角度分布对 p-GaN 厚度的强烈依赖性来解释。本研究中提出的 FDTD 模拟方法有望有利地用于设计具有高 LEE 的 μ-LED 结构。