Sidewall Interface\nNitrogen Treatment for Improving\nGaN-Based Micron-Scale Light-Emitting Diode Efficiency

Defects in the sidewall interfaces are critical to light-emitting\nefficiency of micro-light emitting diodes (μLEDs) for display\napplications. The efficiency decreases sharply when the LED chip size\nis smaller than 10 × 10 μm<sup>2</sup> because the sidewall\ndefect-induced nonradiative recombination process prevails. In this\nwork, we demonstrate the efficiency improvement of GaN-based μLEDs\nwith sizes as small as 4 × 4 μm<sup>2</sup>. Using N<sub>2</sub> plasmon treatment at 250 °C to repair sidewall damage,\nthe light output power of an LED with a mesa size of 4 × 4 μm<sup>2</sup> is improved by 97.29% compared to the reference device without\ntreatment at an injection current density of 25 A/cm<sup>2</sup>.\nAdditionally, compared to a reference device with a mesa area of 100\n× 100 μm<sup>2</sup>, the optical output power density\nof the 4 × 4 μm<sup>2</sup> device shows only a 27.11%\ndrop. To understand the effect of nitrogen plasmon treatment on the\ninterfaces, we conducted EDX (energy-dispersive X-ray spectroscopy)\nand TRPL (time-resolved photoluminescence) analysis on the sidewalls\nof p-type GaN and the quantum well active region. We concluded that\nincorporating nitrogen atoms to repair the dangling bonds and, thus,\na more balanced Ga/N ratio helps reduce defects and thus improve sidewall\nradiative efficiency.