Structural Optimization of Novel MicroLED for Enhanced Performance

Abstract

MicroLED is regarded as a core technology for next-generation displays, but its low light extraction efficiency (LEE) remains a critical bottleneck hindering industrialization. The primary cause of this issue lies in the severe total internal reflection at interfaces between high-index semiconductor layers and surrounding low-index media, which traps a large portion of generated photons within the chip. In this paper, based on the finite-difference time-domain (FDTD) method, which is well-suited for resolving wavelength-scale optical interactions in complex geometries, we systematically investigate the effects of electrode layout, surface microstructure, and mesa geometry on the LEE of flip-chip MicroLED chips. A hybrid mesh electrode achieves an LEE of 39.5% while maintaining good current uniformity. Randomly roughened surfaces and photonic crystal structures improve the LEE to 48.5% and 52.3%, respectively. Furthermore, we compare regular- and inverted-trapezoidal mesa structures. The inverted-trapezoidal structure with a sidewall angle of 10° achieves a peak LEE of 0.38, which is 35% higher than that of the vertical sidewall reference, while the regular-trapezoidal structure with a sidewall angle of 5° reaches 0.30 (5% improvement). The enhanced performance of the inverted-trapezoidal configuration is attributed to the fact that inclined sidewalls help to redirect laterally trapped photons towards the top escape surface by altering the angle of incidence upon internal reflection. Through multi-parameter collaborative optimization based on the inverted-trapezoidal shape, a peak LEE of 64.2% is finally achieved. This work provides a systematic theoretical basis and practical structural optimization strategies for high-performance MicroLED chips.