Abstract
The material systems, the various approaches of the LED's, and the new types of LED's are reviewed. Firstly, the high efficiency of LED is reviewed, and the most used one, (460nm LED+yellow phosphor), is discussed. Secondly, LED with up to 400nm is discussed. Thirdly, InGaN covers all visible spectrums and the white LED's using InGaN are reviewed. The light emission intensity of InGaN is changed with the substrate orientation, and the white LED of InGaN is built. The In-rich InGaN LED is grown, and the reddish color LED is obtained. The high efficiency LED with Cu heat sink is reviewed. And finally, the AC-LED with the heat generation and the sink at exactly the same place is reviewed.
