Improving Optical Efficiency and Luminance of GaN-Based Micro-Light-Emitting Diodes for High-Resolution Displays via NH₃ Plasma Pretreatment

GaN-based micro-light-emitting diodes (Micro-LEDs) are regarded as promising light sources for near-eye-display applications such as augmented reality/virtual reality (AR/VR) displays due to their high resolution, high brightness, and low power consumption. However, the application of Micro-LEDs in high-pixel-per-inch (PPI) displays is constrained by the drop in efficiency caused by sidewall defects in small-sized devices. In this study, a process method involving NH₃ plasma pretreatment to reduce sidewall defects is proposed and investigated for enhancing the external quantum efficiency (EQE) of small-sized devices. The influence of NH₃ plasma pretreatment on the GaN surface is investigated and analyzed by the X-ray photoelectron spectroscopy (XPS) characterizations and compared with H₂ plasma pretreatment for further discussions on the mechanism. The enhancement in EQE and luminance of devices with different sizes by NH₃ plasma pretreatment is observed and discussed. For the 10 μm Micro-LED, a peak EQE of 20.2% is achieved, representing a 33.8% improvement compared with that of the untreated device. At 200 A/cm², the luminance of the 10 μm device with NH₃ plasma pretreatment is 1.64 × 10⁷ cd/m², exhibiting a 49% increase compared with the untreated device.