Sidewall Interface Nitrogen Treatment for Improving GaN-Based Micron-Scale Light-Emitting Diode Efficiency

Defects in the sidewall interfaces are critical to light-emitting efficiency of micro-light emitting diodes (μLEDs) for display applications. The efficiency decreases sharply when the LED chip size is smaller than 10 × 10 μm2 because the sidewall defect-induced nonradiative recombination process prevails. In this work, we demonstrate the efficiency improvement of GaN-based μLEDs with sizes as small as 4 × 4 μm2. Using N2 plasmon treatment at 250 °C to repair sidewall damage, the light output power of an LED with a mesa size of 4 × 4 μm2 is improved by 97.29% compared to the reference device without treatment at an injection current density of 25 A/cm2. Additionally, compared to a reference device with a mesa area of 100 × 100 μm2, the optical output power density of the 4 × 4 μm2 device shows only a 27.11% drop. To understand the effect of nitrogen plasmon treatment on the interfaces, we conducted EDX (energy-dispersive X-ray spectroscopy) and TRPL (time-resolved photoluminescence) analysis on the sidewalls of p-type GaN and the quantum well active region. We concluded that incorporating nitrogen atoms to repair the dangling bonds and, thus, a more balanced Ga/N ratio helps reduce defects and thus improve sidewall radiative efficiency.