Currently, LEDs are applied to various applications including natural color LED display devices, LED traffic signals, white LEDs, and the like. Recently, high-efficiency white LEDs have been expected to replace common fluorescent lamps. Particularly, the efficiency of white LEDs is approaching to the similar level to that of general fluorescent lamps.
In general, a light-emitting diode is formed by growing epitaxial layers on a substrate such as a sapphire substrate, and includes an N-type semiconductor layer, a P-type semiconductor layer, and an active layer interposed therebetween. Meanwhile, an N-type electrode pad is formed on the N-type semiconductor layer and a P-type electrode pad is formed on the P-type semiconductor layer. The light-emitting diode is electrically coupled to an external power source through the electrode pads, and thus is driven. In this case, current flows from the P-type electrode pad to the N-type electrode pad via the semiconductor layers.