A light-emitting diode (LED) is an electronic light source. Discovered in the early 20th century, it eventually was converted to practical use. Today, LEDs can be found in many applications.
Beginnings
H.J. Round, a personal assistant to inventor Guglielmo Marconi in England, published a short article in 1907 reporting on his experimental findings. Using silicon carbide, or carborundum, and cat whiskers, he was able to detect a "bright glow." However, there was no follow-up article, and Round's discovery was largely forgotten for many years.
Oleg Losev
Russian scientist and inventor Oleg Vladimirovich Losev didn't have a formal education and wasn't aware of Round's publication. However, he became the first person to do substantial research on LED. Noticing the light emission produced when current is passed through diodes used in radio receivers, Losev identified the same compound that Round had used two decades ago as a light-emitting diode. Losev's writings from 1924 to 1930 on this observation earned him a Ph.D. in 1938. His work was never put to practical use during his lifetime, and he starved to death in the Siege of Leningrad, Russia, during World War II.
Further Development
The two decades after World War II saw more advances in LED research. In 1955, Rubin Braunstein of Radio Corporation of America (RCA) discovered infrared emission from gallium arsenide (GaAs), among other semi-conductor alloys. Braunstein's work was the foundation for Robert Biard and Gary Pittman. In 1961, these two Texas Instruments employees discovered that when they passed electric current through GaAs, they produced infrared radiation. This led them to receive a patent for the infrared LED, although it was not visible.
Practical Use
The first commercially usable LEDs were developed in 1962, thanks to the work of General Electric Company employee Nick Holonyak, Jr. He invented a way to synthesize gallium arsenide phosphide (GaAsP) that revealed visible light. This was the red LED, and it soon was embraced for use in electronic display devices for watches and radios. With further work through the 1970s, more colors and wavelengths became available.
Today
LEDs are used in all kinds of lighting, including traffic signals, car brake lights, exit signs and household lighting. LED-powered indicators are used for reading CD and DVD discs in computers, video players and game consoles, and LED components are used for transmitting signals from remote controls to such devices. LEDs are also used with semiconductor lasers for broadband telecommunication and the Internet.
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