Role of Sidewall Conditions in the External Quantum Efficiency of InGaN-Based Micro-LEDs

This study aims to investigate the external quantum efficiency (EQE) of InGaN-based blue micro light-emitting diodes (μLEDs) depending on sidewall conditions and current stress. To this end, this study prepares two sets of InGaN blue μLEDs with sizes of 10 × 10 μm², 20 × 20 μm², and 40 × 40 μm²: 1) μLEDs with and without a 10 nm-thick ALD-SiO₂ interlayer and 2) μLEDs with varying atomic layer deposition (ALD)-Al₂O₃ passivation layer thickness and tetramethylammonium hydroxide (TMAH) treatment time. The results of set 1 demonstrate that the ALD-SiO₂ interlayer layer has a significant effect on the EQE of μLEDs only at low current densities, as the interlayer effectively protects against subsequent plasma damage. The results of current stress show that the ALD-SiO₂ interlayer plays an important role at low current densities. The results of set 2 demonstrate that a sufficiently thick ALD passivation layer should be deposited to minimize sidewall interface states, and a short TMAH treatment time of 1 min is sufficient. The results in this study highlight that sidewall conditions have a substantial impact on the EQE at low current densities and indicate that optimizing ALD thickness and TMAH treatment time can reduce processing time and cost.