Performance analysis of GaN-based micro light-emitting diodes by laser lift-off process

Abstract

In this study, a monochromatic GaN-based micro-light-emitting-diode (µLED) array was fabricated using flip-chip technology. The laser lift-off (LLO) process was employed to decrease the light divergence caused by the differing refractive indexes of sapphire (n = 1.77) and GaN (n = 2.4). The LLO-µLEDs considerably improve light collimation, compared with conventional flip-chip µLEDs containing a sapphire substrate. We highlight, in particular, the importance of the optical characteristics before and after LLO. Collimation of light was discovered to be 12% higher after removal of the sapphire substrate. The results are of high importance for understanding the optical properties of µLED arrays after LLO. Keywords: GaN, Light-emitting diodes, Laser lift-off, Micro-LEDs