Effect of Varied Undoped GaN Thickness on ESD and Optical Properties of GaN-Based LEDs

The optical property and electrostatic discharge (ESD) endurance of GaN-based light-emitting diodes (LEDs) with varied undoped GaN thickness are studied and demonstrated. As the undoped GaN thickness increased, the generation of V-shaped defects in the active region was suppressed. Therefore, the output power for a 6-μ.m-thick undoped GaN layer would be enhanced remarkably due to the reduction of nonradiative recombination ratio within the active region. On the other hand, under a reverse ESD pulse voltage of 5.5 kV, the survival rate of the LEDs with an undoped GaN layer thickness of 1.5, 4, and 6 μm were 75%, 65%, and 55%, respectively. It was found that the ESD endurance for a 1.5-μ.m-thick undoped GaN layer with higher internal capacitance was obviously better than others. This could be related to the built-in electric field of LEDs induced by spontaneous polarization field.