研究目的
Investigating the optical properties and performance of GaN-based micro-light-emitting-diode (μLED) arrays fabricated using flip-chip technology and the laser lift-off (LLO) process.
研究成果
The LLO process successfully improved light collimation by 12% after removing the sapphire substrate, which is crucial for the fabrication of displays with pixel pitch less than 10 μm, as required in AR microdisplays. However, the luminance decreased by approximately 30%, indicating areas for further optimization.
研究不足
The luminance was discovered to be approximately 30% lower after the LLO, possibly due to current leakage or a reduced critical angle causing larger total internal reflection. The LLO process may also increase dislocation concentration, damaging the device.
1：Experimental Design and Method Selection:
The study employed flip-chip technology and the LLO process to fabricate μLED arrays. The LLO process was used to remove the sapphire substrate to improve light collimation.
2：Sample Selection and Data Sources:
GaN LED epilayers were grown on a 2-inch c-plane sapphire substrate using metal organic chemical vapor deposition (MOCVD).
3：List of Experimental Equipment and Materials:
MOCVD for epitaxial growth, ICP-RIE for patterning GaN, excimer laser for LLO process, and KEITHLEY 236 for measuring reverse current–voltage characteristics.
4：Experimental Procedures and Operational Workflow:
The fabrication process included patterning GaN, depositing ohmic contacts, passivation, bump metal deposition, flip-chip bonding, and LLO process.
5：Data Analysis Methods:
Light intensity profiles were measured using ImageJ TM software, and electroluminescence spectra were obtained using a PR-670 spectrophotometer.
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