LED light source is LED by ⅲ-ⅳ-ⅵ compounds such as GaAs (gallium arsenide), GaP (gallium phosphide), GaAsP (p gallium arsenide) semiconductors made of, its core is the PN junction. Therefore it has a p-n junction I-v characteristics, which are conducting, reverse, breakdown characteristic. In addition, under certain conditions, it also has optical properties. Under the forward voltage, electronic injection by n p, hole injection by p n. Access to other areas of minority-carrier (small) part of majority carriers (multi) light is a composite. Assumes that the light is in p, then directly injected electrons and the valence band holes light is a composite, or were captured by luminescent centers first, then hole recombination. Apart from this compound, and some electrons are non-luminescent Center (near the center between the conduction band and the middle) capture and then compounded with holes, each time the energy released is small, visible light cannot be formed. Content of the glow relative to the larger the ratio of non-light emitting compound, optical quantum efficiency is higher. Because the compound is in the area of minority carrier diffusion of light, so only close to the PN junction number μ m or less.