Sidewall defect suppression of 620 nm AlGaInP-based red µLED devices using HfO₂ ALD passivation

Micro light-emitting diodes (µLEDs), crucial for advanced displays and communication systems, face efficiency challenges due to sidewall defects. This study investigates the impact of various passivation layers, including SiO₂, Al₂O₃, and HfO₂, on AlGaInP-based 620 nm red µLEDs. We fabricated devices with two mesa sizes and demonstrated that atomic layer deposition (ALD) passivation, especially with HfO₂, significantly enhances performance. HfO₂ passivation shows improvement in external quantum efficiency (EQE) by up to 57.9% for a 13 × 20 µm² device size and 43.9% for a 26 × 40 µm² device size, compared to µLEDs with SiO₂. Furthermore, it reduces surface recombination velocity (SRV) by 19.7% compared to SiO₂. These findings highlight the potential of HfO₂, via ALD, in advancing µLED technology by improving efficiency and performance through effective defect mitigation.