Insight on Self-Emissive μLED Display from Correlations between Surface Current and Efficiency/Emission Properties of Size-Dependent μLEDs

Abstract

III–V semiconductor-based micro-light-emitting diodes (μLEDs) have emerged as a promising candidate for next-generation displays, particularly in near-eye display (NED) applications. However, several physical constraints, including size-dependent efficiency degradation, color purity, and emission uniformity, pose significant challenges to the commercialization of μLED displays. This study investigates the underlying factors contributing to these limitations, focusing on the surface current behavior of the μLEDs. By examination of the size-dependent electrical and optical properties, as well as the emission behaviors of nitride-based blue, green, and red (RGB), as well as phosphide-based red μLEDs, correlations between surface current behavior and size-dependent efficiency degradation of μLEDs are established. The findings strongly suggest that the inhibition of carrier migration to the sidewall is the key to addressing the size-dependent efficiency degradation. However, our analysis of the emission behaviors reveals that carrier localization-induced size-immunity properties in nitride-based green and red μLEDs may benefit the size-dependent efficiency but not as a display pixel due to the nonuniform emission patterns. These results indicate that the degree of size-dependent efficiency degradation is not the sole criterion for consideration of RGB subpixels. This analysis provides insights into the surface current characteristics of both nitride-based and phosphide-based μLEDs, offering strategies to overcome the identified physical constraints.