Mechanisms and Performance Analysis of GaN-Based Micro-LED Grown on Pattern Sapphire Substrate by Laser Lift-Off Process

The laser lift-off (LLO) process was employed to fabricate a monochromatic GaN-based green micro-light-emitting-diode (Micro-LED) 14 x 14 arrays grown on pattern sapphire substrate (PSS) in this research. A new experimental phenomenon and internal mechanism of some epitaxial residues on the top and sidewalls of PSS protrusion after laser stripping were deeply discussed. In addition, the reasons for the formation of micro lattice dislocation of epitaxial layer crystal caused by laser were also analyzed. The leakage current of the array devices after LLO was 200 times higher that before LLO under the same voltage, but the light output current efficiency was discovered to be 109.7% higher under the 500 cd m(-2) brightness. The results indicate peak wavelength was blue shift 3 nm once the LLO process had been performed. Furthermore, the optical pattern from a "heart-shaped" distribution before LLO was changed into the maximum intensity directly above the array devices. The luminous angle was also reduced from +/- 75 degrees to +/- 65 degrees, which indicates that the collimation of the light after LLO process was increased. The results are high important for understanding the optical properties of Micro-LED array devices after LLO process.