BY STEPHEN EVANCZUK
Lighting-emitting diodes (LED) pervade nearly every electrically operated device, broadly serving functions ranging from power-status display to general illumination. With continuing advances in their capabilities and characteristics, LEDs have emerged as the dominant light source not only in electronic equipment but also replacing traditional incandescent and fluorescent lamps in every conceivable application.
Electrically, an LED is simply a semiconductor diode comprising a p-n junction where the p side, or anode, contains excess positive charge (holes) and the n side, or cathode, contains excess negative charge (electrons). The application of a forward voltage across the p-n junction causes electrons to move from the n area toward the p area and holes to move toward the n area. Near the junction, the electrons and holes combine with the release of energy as photons, resulting in the light emitted by the LED.