Omnidirectional color shift suppression of full-color micro-LED displays with enhanced light extraction efficiency

The three-primary-color chip array is the most straight-forward to realize full-color micro-LED displays. However, the luminous intensity distribution shows high inconsistency between the AlInP-based red micro-LED and GaN-based blue / green micro-LEDs, resulting in the issue of angu-lar color shift with different viewing angles. This Letter analyzes the angular dependence of color difference of con-ventional three-primary-color micro-LEDs, and proves that the inclined sidewall with homogeneous Ag coating has a limited angular regulation effect for micro-LEDs. Based on this, a patterned conical microstructure array is designed on the micro-LED's bottom layer to effectively eliminate the color shift. This design cannot only regulate the emis-sion of full-color micro-LEDs to perfectly meet Lambert's cosine law without any external beam shaping elements, but also improve the light extraction efficiency of top emission by 16%, 161%, and 228% for red, green, and blue micro -LEDs, respectively. The color shift increment u ' v ' of the full-color micro-LED display is also kept below 0.02 with the view-ing angle ranging from 10 degrees to 90 degrees.(c) 2023 Optica Publishing Group