Study of laser-debonded GaN LEDs

Detailed investigations of laser-debonded GaN-based light-emitting diodes (LEDs) grown by metal-organic chemical vapor deposition (MOCVD) on sapphire substrates were reported. The debonded surface was roughened by photoelectrochemical (PEC) etching in a mixture of potassium hydroxide (KOH) and peroxydisulfate (K2S2O8) solution. The power for the laser-assisted debonding process has been systematically optimized. The data show that as long as the laser power does not exceed the optimal value, there is no degradation in the current-voltage (I-V) characteristics, the brightness, as well as the low-frequency noise properties of the devices. The roughness of the debonded surface is systematically varied using different etching times. Experimental results demonstrate strong dependencies of the luminous intensity of the device on the roughness of the debonded surface. A 60% improvement in the luminous intensity of the debonded and roughened LED compared to the original on-sapphire device was observed. This increase in the extraction efficiency is attributed to the reduction in the total internal reflection at the roughened GaN/air interface.