Degradation behaviors and reliability of high power GaN-based white LEDs with different structures

Highly stress tests were carried out for GaN-based high power white LEDs with different structures, including traditional lateral, vertical as well as flip-chip LEDs. During the tests, all the electrical, optical and thermal properties were measured in-situ for each LED. The results show that for lateral LEDs, the structure property of LED epitaxial layer is still the key factor that influences the optical degradation behavior. With similar structure properties and leakage current, the failure mechanism will be similar and the activation energy is close to each other. In addition, it is shown that the vertical and flip-chip LEDs can improve the heat dissipation effectively, especially at high temperature. Compared the lifetimes of the LEDs with different structures at different stress temperatures, it can be found that the stress temperature play an important role for reliability evaluation. The optimized stress temperature can help to evaluate the reliability more efficiently. The study will give guidance for the future LED design with controllable lifetime. A statement of the problem or situation, and the approach that is taken to resolve it. The second paragraph in the Section should start with a "line break" (using the enter/return key), but do not add an extra blank line. The slight indent will clearly define the paragraphs, and the "ECTC Text" Style includes a slight spacing (1 point) between paragraphs within the Section. This first Section may also contain a summary of the past developments and background of what is already known, and published elsewhere. This is best summarized in your own paper, with references to other publications containing more-extensive discussions of this background information. [1] The references are placed at the end of the paper. [2] Remember that you should not re-state material that is readily available in the archival literature; simply summarize it, then add a reference or two. Many peer-reviewed papers in our fields have been published in the IEEE Transactions on Components and Packaging Technologies, and on Advanced Packaging — see www.cpmt.org/trans/.