Effect of Residual Stress of Thin and Thick Layers on Laser Lifted-Off Light Emitting Diodes

The mechanical stability and optical performance of vertical structure GaN-based light emitting diodes (LEDs) were investigated in company with the analysis of residual stresses of layer components constituting LED structure. Residual stress of a PR passivation structure, an Au seed layer, and an electrodeposited Cu substrate was measured according to the layer thickness that is the most important parameter to affect the residual stress. They were formed covering the whole LED wafer, which includes many isolated vertical LED chip structures. It was concluded that their residual stresses according to the layer thickness influenced critically the mechanical damage and light output power of vertical LED structures after the laser lift-off (LLO) of a sapphire substrate. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3610360] All rights reserved.