The structure at the atomic scale and optical properties of GaN-based green light-emitting diodes (LEDs) before and after in situ degradation were investigated by spherical aberration corrected scanning transmission electron microscopy and temperature-dependent micro-photoluminescence. Indium (In) interstitial atoms existed in the degraded sample, due to the small-bond-energy In atoms deviating from their normal lattice position, caused by the relaxation of the InGaN well. Both the peak wavelengths of the original and degraded green LEDs had similar temperature-dependent behaviors, due to the localization states in the InGaN well. These wavelengths indicate that the degradation had little influence on the localization states. However, the emission peak of the degraded green LED redshifted by 1.6 nm at 300 K, and the integrated intensity decreased by 36.8%, compared to the peak and intensity of the original sample, respectively. Based on first-principles calculations, the calculated bandgap for the relaxation of the InGaN well was small. Therefore, the wavelength redshifted, and the luminous efficiency of the green LED decreased after degradation. These features are attributed to a decreased bandgap due to the relaxation of the InGaN well; increased defect density, resulting from In interstitial atoms; and an increase in the InGaN well thickness.

中文翻译：

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原位降解对GaN基绿色发光二极管原子结构和光学性能的影响

通过球差校正扫描透射电子显微镜和温度相关的微光致发光研究了原位降解前后 GaN 基绿色发光二极管 (LED) 的原子尺度结构和光学特性。由于 InGaN 阱的弛豫导致小键能 In 原子偏离其正常晶格位置，因此降解样品中存在铟 (In) 间隙原子。由于 InGaN 阱中的局部化状态，原始和退化绿色 LED 的峰值波长都具有类似的温度相关行为。这些波长表明降解对定位状态几乎没有影响。然而，退化的绿色 LED 的发射峰在 300 K 时红移了 1.6 nm，与原始样品的峰值和强度相比，积分强度分别下降了 36.8%。根据第一性原理计算，计算出的 InGaN 阱弛豫的带隙很小。因此，波长发生红移，绿色LED退化后发光效率下降。这些特征归因于 InGaN 阱的弛豫导致带隙减小；由间隙原子引起的缺陷密度增加；以及 InGaN 阱厚度的增加。这些特征归因于 InGaN 阱的弛豫导致带隙减小；由间隙原子引起的缺陷密度增加；以及 InGaN 阱厚度的增加。这些特征归因于 InGaN 阱的弛豫导致带隙减小；由间隙原子引起的缺陷密度增加；以及 InGaN 阱厚度的增加。