"I wanted to work in the visible spectrum... and everybody else was working in the infrared."
Nick Holonyak
The LED (light-emitting- diode) is a semiconductor device. All semiconductors have a variable ability to conduct electric current because of impurities (caused by trace chemical additives) in their structure. An N-type impurity adds an extra electron to the semiconductor, and a P-type impurity provides an electron hole. Electrons, negatively charged particles, naturally move from areas with many electrons (negative) to areas with few electrons (positive).
In a diode, an N-type material is placed next to a. P-type one, and the two are sandwiched between electrodes. This setup only allows electric current (a stream of electrons) to flow in one direction, from the N-type side's electrode to the P-type side's electrode.
When an electron drops into an electron hole, it releases energy in the form of a photon. As a result, when electrons move from one side of the diode to the other, light is released. Depending on the types of materials used in the semiconductor, different wavelengths of light are produced.
In 1962 Nick Holonyak (b. 1928) created a diode made of his synthetic gallium arsenide phosphide crystals; this produced visible light, making it the first visible-spectrum LED. Using similar principles, he also constructed a semiconductor laser prototype that was a precursor to the CD-reading lasers of today.
LEDs are used in digital clocks, watches, televisions, traffic lights, and display screens for many electronic devices. Infrared LEDs are used in remote controls. Because LEDs create less waste heat energy than conventional bulbs, they are also used in power- efficient lighting systems, lamps, or flashlights.
