Impact of sidewall passivation on reliability in InGaN-based micro-LEDs

The performance degradation of micro light-emitting diodes (micro-LEDs) is closely associated with the deterioration of sidewall passivation layers under prolonged electrical bias. We investigate reliability improvements in 20 μm×20 μm InGaN/GaN blue micro-LEDs by suppressing the formation of an unstable interfacial layer during sidewall passivation. SiO2 is deposited on the etched mesa sidewalls using either Sputtering or plasma-enhanced chemical vapor deposition (PECVD). Comparative analysis reveals that PECVD-passivated devices experience more severe performance degradation, primarily due to the increased leakage current. After 100 h of accelerated aging, external quantum efficiency decreases by 44% in PECVD-passivated samples, whereas Sputter-passivated devices exhibit only an 11% reduction. This discrepancy is attributed to the formation of a thicker and chemically unstable gallium oxynitride (Ga-OX-N1−X) interfacial layer at the SiO2/GaN-based interface, which facilitates the generation of sidewall defects. Suppressing the formation of this interlayer enhances the crystallinity and structural stability of the passivation layer, thereby mitigating the activation of point defects. Notably, Sputter deposition is more effective in minimizing the formation of Ga–O–N interlayer. These findings emphasize the critical role of achieving low-defect-density sidewall passivation to improve the reliability of micro-LEDs for next-generation high-resolution display applications.