Temperature-Dependent Carrier Dynamics in Micro-LEDs With Different Sidewall Passivation Layers

In this work, we investigated the impact of different passivation techniques on carrier recombination mechanisms in micro-LEDs. Five distinct passivation processes—SiO2, Al2O3, a combination of Al2O3 and SiO2, Si3N4, and a combination of Si3N4 and Al2O3—were employed to fabricate devices of various sizes. Optical spectrometer measurements, spatially resolved electroluminescence (EL) mapping, and quantum efficiency-current density analysis demonstrated that atomic layer deposition (ALD)-Al2O3 passivation exhibited superior suppression of p-GaN surface defects, whereas plasma-enhanced chemical vapor deposition (PECVD)-SiO2 showed enhanced effectiveness in mitigating sidewall defects. Devices employing these two passivation schemes achieved optimal performance overall. Temperature-dependent EL characterization revealed more pronounced thermal effects on p-GaN surface defects than on sidewall defects. Consequently, SiO2-passivated devices demonstrated superior performance at low temperatures, while Al2O3-passivated devices excelled at elevated temperatures. These findings provide valuable insights into the passivation mechanisms of defects in micro-LEDs and shed light on the optimization of micro-LED device design processes. Our results highlight the importance of selecting appropriate passivation materials based on operating conditions to maximize device performance.