Efficiency improvement of AlGaInP-based red micron-scale light-emitting diodes using sidewall steam oxidation

Although micro-LED displays are considered emerging display technology, their micron-scale LED chip size suffers from significant efficiency degradation, which affects the display's power budget. The low light output efficiency is mainly attributed to an increased weighting of sidewall nonradiative recombination with the perimeter-area ratio of smaller chip size. To prevent carrier recombination in the dry-etching induced sidewall defects, we, in this study, introduce insulting regions in the mesa sidewall of the red LED. The insulting regions were created by oxidizing the metal components in the epi-structures. When the chip sizes of 100 × 100, 50 × 50, and 25 × 25 μm² are compared, our steam oxidation technique efficiently suppresses sidewall current flow and nonradiative recombination. The suppression is more obvious for a smaller mesa size. For a 25 × 25 μm² LED mesa, optical output power density increases by 31.4% compared to a device without oxidation. Additionally, under 20 A/cm² injection, a 25 × 25 μm² LED with sidewall oxidation shows only an 11.3% reduction in output power density compared to a larger 100 × 100 μm² device without oxidation. These results highlight the potential of sidewall oxidation in overcoming efficiency degradation issues for micro-red LEDs in displays.