Mitigating sidewall damage effects in GaN-based multi-quantum-well micro-LEDs prepared by top-down fabrication

초록

This review examines the sidewall damage effects in GaN-based micro- and nano-light emitting diodes (mu LEDs/nLEDs) fabricated via top-down inductively coupled plasma reactive ion etching. We analyze the structural and electronic properties of etched surfaces, damage mitigation strategies through process optimization, and postetch treatments. Furthermore, we evaluate models explaining performance degradation with a decrease in device dimensions. Blue InGaN/GaN mu LEDs exhibit severe efficiency degradation below similar to 20 mu m diameter (the 'efficiency cliff'), whereas green and red devices show greater resilience. We attribute this behavior to differences in surface recombination velocity, carrier diffusion length, and localization effects. Surface treatments including tetramethylammonium hydroxide etching, (NH4)2S passivation, hydrogen plasma treatment, and atomic layer-deposited dielectrics significantly mitigate damage. Deep-level transient spectroscopy reveals nitrogen interstitial (Ni) acceptors near EC-1 eV and gallium vacancy (VGa) complexes near EV + 0.8 eV as the dominant recombination centers. The damaged region extends 0.5-1 mu m from sidewalls-significantly beyond the structurally damaged zone (similar to 40-100 nm). Emerging approaches, such as neutral beam etching and localized surface plasmon coupling, show promise for achieving high efficiency in sub-5 mu m devices required for advanced display applications.

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