Improving Optical Efficiency and Luminance of GaN-Based Micro-Light-Emitting Diodes for High-Resolution Displays via NH 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 NH plasma pretreatment to reduce sidewall defects is proposed and investigated for enhancing the external quantum efficiency (EQE) of small-sized devices. The influence of NH plasma pretreatment on the GaN surface is investigated and analyzed by the X-ray photoelectron spectroscopy (XPS) characterizations and compared with H plasma pretreatment for further discussions on the mechanism. The enhancement in EQE and luminance of devices with different sizes by NH 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/cm, the luminance of the 10 μm device with NH plasma pretreatment is 1.64 × 10 cd/m, exhibiting a 49% increase compared with the untreated device.