Ultrafast Laser Lift-off of Semipolar GaN-based LEDs on Sapphire Substrates

The poor substrate conductivity and thermal properties have been a big challenge for GaN-based LEDs grown on sapphire substrates. Utilizing laser lift-off technology to transfer GaN-based LEDs from sapphire substrates to alternative substrates has emerged as an effective solution. This paper employed ultrafast picosecond laser to detach semi-polar GaN-based LEDs overgrown on patterned sapphire substrates and successfully transfered them to Si substrates，forming vertical structure LED devices. SEM measurements revealed that at a laser energy density of 1. 3 J/cm2，efficient decomposition of the sapphire and GaN interface occurred，minimizing adverse effects on the devices. Raman spectroscopy results demonstrated effective stress release in the GaN layer，in which the residual stress decreases from 1. 42 GPa to 0. 29 GPa. I-V measurements of the fabricated vertical structure LEDs showed an increase in forward current from 0. 164 mA to 0. 759 mA at 5 V voltage，along with an enhancement in photolumines-cence and electroluminescence performances. This study presents experimental research on ultrafast laser lift-off of semi-polar GaN-based LEDs on sapphire substrates，providing support for the development of low-damage，high-efficiency transfer technologies. It holds promise in accelerating the advancement and application of semi-polar GaN-based LEDs. © 2024 Editorial Office of Chinese Optics. All rights reserved.