A light-emitting diode, commonly referred to as an LED, is a simple semiconductor device that uses little energy to release light when a current passes through it. The wavelength of light emitted depends on what material is used to make up the semiconductor crystals of the LED. The visible light emitting LED is most often used in alphanumeric displays where low-energy use is essential. The infrared emitting LED is most often used in remote control mechanisms.

The basic technology involved in the LED is the same as that which applies to all diodes. A diode is a simple rectifier that allows electricity to flow in one direction only. The first diodes were vacuum tubes in which electrons freed from the cathode would be attracted by the anode through a metal plate only when the anode is positively charged. The semiconductor diode consisting of two terminals and...