Origin of the Inhomogeneous Electroluminescence of GaN-Based Green Mini-LEDs Unveiled by Microscopic Hyperspectral Imaging,ACS Photonics

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Origin of the Inhomogeneous Electroluminescence of GaN-Based Green Mini-LEDs Unveiled by Microscopic Hyperspectral Imaging
ACS Photonics ( IF 6.5 ) Pub Date : 2022-10-18 , DOI: 10.1021/acsphotonics.2c01197
Xi Zheng ₁ , Weijie Guo ₁ , Changdong Tong ₁ , Peixin Zeng ₁ , Guolong Chen ₁ , Yulin Gao ₁ , Lihong Zhu ₁ , Yayong Chen ₂ , Shirui Wang ₃ , Zhiyang Lin ₃ , Yijun Lu ₁ , Zhong Chen ₁

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Although high quantum efficiency has been achieved in large-sized InGaN/GaN LEDs operating at relatively high current densities (above 35 A/cm²), the operating current density of mini-LEDs (around 1 A/cm²) is far less than that of traditional large-sized LEDs. The low external quantum efficiency (EQE) of mini-LEDs at small current densities seriously hinders their practical applications, highlighting the importance of investigating the radiative recombination mechanisms of mini-LEDs at small current densities. By using microscopic hyperspectral imaging, the cryogenic electroluminescence (EL) of GaN-based green mini-LEDs mainly originating from localized excitons was demonstrated experimentally. Based on the dependence of electron–phonon coupling on current and temperature, Coulomb screening of the polarization field weakens the electron–phonon coupling, whereas the band-filling effect enhances the coupling. Coulomb screening of the polarization field can also reduce the deviation of the localization. The EL from edge regions of the mesa adjacent to the sidewall possesses relatively higher peak energy due to the strain relaxation. Results of this work also suggest that optimization of the chromatic characteristics and efficiency can be achieved by strain engineering of GaN-based green mini-LEDs.

中文翻译：

显微高光谱成像揭示 GaN 基绿色 Mini-LED 非均匀电致发光的起源

^{尽管在相对高电流密度（高于 35 A/cm 2} ）下工作的大尺寸 InGaN/GaN LED 已经实现了高量子效率，但 mini-LED 的工作电流密度（约 1 A/cm ²)远低于传统大尺寸LED。mini-LED 在小电流密度下的低外量子效率 (EQE) 严重阻碍了它们的实际应用，凸显了研究 mini-LED 在小电流密度下辐射复合机制的重要性。通过使用显微高光谱成像，实验证明了主要源自局域激子的基于 GaN 的绿色 mini-LED 的低温电致发光 (EL)。基于电子-声子耦合对电流和温度的依赖性，极化场的库仑屏蔽削弱了电子-声子耦合，而能带填充效应增强了耦合。极化场的库仑筛选也可以减少定位的偏差。由于应变松弛，来自与侧壁相邻的台面边缘区域的 EL 具有相对较高的峰值能量。这项工作的结果还表明，可以通过 GaN 基绿色 mini-LED 的应变工程来优化色彩特性和效率。

更新日期：2022-10-18

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