近日，沙特阿拉伯阿卜杜拉国王科技大学的Xiaohang Li及其研究团队取得一项新进展。经过不懈努力，他们实现了InGaN绿色微型LED的无蚀刻像素清晰度。相关研究成果已于2024年5月24日在国际知名学术期刊《光：科学与应用》上发表。

据悉，传统的等离子体蚀刻工艺用于确定微型LED像素可能导致严重的侧壁损伤。靠近侧壁区域的缺陷作为非辐射复合中心和电流泄漏路径，严重恶化器件性能。

在这项研究中，研究人员展示了一种新的选择性热氧化(STO)方法，该方法可以在不经历等离子体损伤和随后介电钝化的情况下实现像素清晰度。在环境空气中进行的热退火氧化过程不仅重塑了LED结构，包括p层和InGaN/GaN多量子阱，同时也对预沉积的SiO₂层下的像素区域实施了精确且有效的选择性保护。

研究结果显示，延长热退火时间可以显著增强氧化物的绝缘性能，大幅降低LED的漏电流。此外，应用较厚的SiO₂保护层能够有效降低器件电阻，进而提高器件效率。研究人员利用STO方法，制备了50 μm、30 μm和10 μm像素尺寸的InGaN绿色微型LED阵列并对其进行了表征。结果表明，在空气退火4h后，在3.5 μm SiO₂保护层下，10 μm像素阵列在10V电压下的泄漏电流密度为1.2×10^-6A/cm²，晶上外量子效率峰值约为6.48%。

这项工作表明，STO方法可以成为未来微型LED制造的有效方法，以减轻等离子体蚀刻引起的LED效率尺寸不利影响，并提高器件效率。通过STO方法制造的微型LED在微型显示器、可见光通信和基于光互连的存储器等领域展现出广阔的应用前景。其近乎平面的像素几何形态为驱动电路与微型LED的单片集成提供了更多可能性。此外，STO方法不仅适用于微型LED的制造，还可扩展到其他III-氮化物器件如光电探测器、激光二极管、高电子迁移率晶体管和肖特基势垒二极管的设计与制造中。

附：英文原文

Title: Etching-free pixel definition in InGaN green micro-LEDs

Author: Liu, Zhiyuan, Lu, Yi, Cao, Haicheng, Maciel Garcia, Glen Isaac, Liu, Tingang, Tang, Xiao, Xiao, Na, Aguileta Vazquez, Raul, Nong, Mingtao, Li, Xiaohang

Issue&Volume: 2024-05-24

Abstract: The traditional plasma etching process for defining micro-LED pixels could lead to significant sidewall damage. Defects near sidewall regions act as non-radiative recombination centers and paths for current leakage, significantly deteriorating device performance. In this study, we demonstrated a novel selective thermal oxidation (STO) method that allowed pixel definition without undergoing plasma damage and subsequent dielectric passivation. Thermal annealing in ambient air oxidized and reshaped the LED structure, such as p-layers and InGaN/GaN multiple quantum wells. Simultaneously, the pixel areas beneath the pre-deposited SiO₂ layer were selectively and effectively protected. It was demonstrated that prolonged thermal annealing time enhanced the insulating properties of the oxide, significantly reducing LED leakage current. Furthermore, applying a thicker SiO₂ protective layer minimized device resistance and boosted device efficiency effectively. Utilizing the STO method, InGaN green micro-LED arrays with 50-, 30-, and 10-μm pixel sizes were manufactured and characterized. The results indicated that after 4h of air annealing and with a 3.5-μm SiO₂ protective layer, the 10-μm pixel array exhibited leakage currents density 1.2×10^-6A/cm² at 10V voltage and a peak on-wafer external quantum efficiency of ~6.48%. This work suggests that the STO method could become an effective approach for future micro-LED manufacturing to mitigate adverse LED efficiency size effects due to the plasma etching and improve device efficiency. Micro-LEDs fabricated through the STO method can be applied to micro-displays, visible light communication, and optical interconnect-based memories. Almost planar pixel geometry will provide more possibilities for the monolithic integration of driving circuits with micro-LEDs. Moreover, the STO method is not limited to micro-LED fabrication and can be extended to design other III-nitride devices, such as photodetectors, laser diodes, high-electron-mobility transistors, and Schottky barrier diodes.

DOI: 10.1038/s41377-024-01465-7

Source: https://www.nature.com/articles/s41377-024-01465-7