For bias stress reliability testing, InGaN/GaN MQW blue LEDs with different barrier thicknesses were grown by metalorganic chemical vapor deposition. Fast-Fourier-transformed high-resolution transmission electron microscopy was used to analyze the influence of the bias stress reliability with the strain status in the barrier layer. A comparison of the (1 (1) over bar 00) planar distances showed that a thicker thickness of the barrier layer induced the relaxation of stored strain. A thinner barrier thickness led to the reduced formation of misfit dislocations, which was responsible for the improvement of bias stress reliability of LEDs. These results indicated the importance of delicate control of stored strain in nitride films for improving the reliability and lifetimes of devices. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.059202jes] All rights reserved.