Abstract
The behavior of the related reliability of InGaN-based blue and green LED chips were investigated with 20,40,60 mA constant current stress up to 424 h at room temperature. Under 60mA constant current stress,the green LED chip showed more prominent optical power degradation at low measuring current levels than high measuring current levels. While,the blue LED chip showed the consistent optical power decrease at different measuring current levels. It should be pointed out that,at high measured current levels( 20 mA),blue and green LED chips expressed similar optical degradation( 18%) after the aging tests. Meanwhile,the aging stress does not significant affect the forward-bias electrical characteristics of blue and green LED chips,which indicated the similar degradation process in some aging tests. It is believed that the induced defects in blue LED by electrical stress mainly contribute to the nonradiative recombination centers,while in green LED chip the defects contribute to the localized leakage paths rather than the nonradiative recombination centers.Based on the mechanism analysis of blue and green LED,the design of GaN based epitaxial structure was optimized,and the thickness of quantum barrier was reduced to weaken the internal electrical field in the active layer to improve the reliability of LED.
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