Effect of in situ degradation on the atomic structure and optical properties of GaN-based green light-emitting diodes
Effect of in situ degradation on the atomic structure and optical properties of GaN-based green light-emitting diodes
复制标题
DOI：
10.1063/5.0021659
复制
发表时间：
2020-11-23
影响因子：
4
通讯作者：
Xu, B.
中科院分区：
文献类型：
--
作者：
Liu, Q.;Han, D.;Xu, B.
采用球差校正扫描电子显微镜和变温显微光致发光技术研究了原位退化前后GaN基绿色发光二极管(LED)的原子级结构和光学性质。In(In)间隙原子存在于退化样品中，这是由于InGaN势垒驰豫导致原子中的小键能偏离其正常晶格位置所致。由于InGaN势垒中的局域态，原始和退化的绿色发光二极管的峰值波长都具有相似的温度依赖行为。这些波长表明，退化对局域态的影响很小。而降解后的绿色发光二极管在300K时发射峰红移1.6 nm，积分强度比原始样品的峰值和强度分别降低了36.8%。基于第一性原理计算，计算得到的InGaN势垒弛豫带隙很小。因此，波长红移，绿色LED的发光效率在退化后下降。这些特征归因于InGaN势垒弛豫导致的带隙减小，间隙原子中的缺陷密度增加，以及InGaN势垒厚度的增加。
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 1.6nm at 300K, 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.