What is an LED?
LEDs are semiconductor diodes, electronic devices that permit current to flow in only one direction. The diode is formed by bringing two slightly different materials together to form a PN junction (Figure 2). In a PN junction, the P side contains excess positive charge (“holes,” indicating the absence of electrons) while the N side contains excess negative charge (electrons).
|Figure 2. A simplified PN junction diagram.|
When a forward voltage is applied to the semiconducting element forming the PN junction (heretofore referred to as the junction), electrons move from the N area toward the P area and holes move toward the N area. Near the junction, the electrons and holes combine. As this occurs, energy is released in the form of light that is emitted by the LED.