Light-emitting diode

LEDLEDslight emitting diodesLED lightslight-emitting diodesblue LEDLight Emitting DiodeLED lightingRGB LEDLight-emitting diode (LED)
A light-emitting diode (LED) is a semiconductor light source that emits light when current flows through it.wikipedia
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Automotive lighting

taillightturn signalturn signals
LEDs are used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, camera flashes, lighted wallpaper, plant growing light, and medical devices.
In 1993, the first LED tail lamps were installed on mass-production automobiles.

Silicon carbide

carborundumSiCSiC-MOSFET
Electroluminescence as a phenomenon was discovered in 1907 by the British experimenter H. J. Round of Marconi Labs, using a crystal of silicon carbide and a cat's-whisker detector.
Electronic applications of silicon carbide such as light-emitting diodes (LEDs) and detectors in early radios were first demonstrated around 1907.

H. J. Round

Henry Joseph RoundH.J. RoundCaptain H. J. Round
Electroluminescence as a phenomenon was discovered in 1907 by the British experimenter H. J. Round of Marconi Labs, using a crystal of silicon carbide and a cat's-whisker detector.
He was the first to report observation of electroluminescence from a solid state diode, leading to the discovery of the light-emitting diode.

Semiconductor

semiconductorssemiconductingsemiconductor material
A light-emitting diode (LED) is a semiconductor light source that emits light when current flows through it.
In 1906 H.J. Round observed light emission when electric current passed through silicon carbide crystals, the principle behind the light-emitting diode.

Oleg Losev

O. V. LosevOleg Vladimirovich Losev
Russian inventor Oleg Losev reported creation of the first LED in 1927.
He observed light emission from carborundum point-contact junctions, the first light-emitting diode (LED), did the first research on them, proposed the first correct theory of how they worked, and used them in practical applications such as electroluminescence.

James R. Biard

In September 1961, while working at Texas Instruments in Dallas, Texas, James R. Biard and Gary Pittman discovered near-infrared (900 nm) light emission from a tunnel diode they had constructed on a GaAs substrate.
Some of his more significant patents include the first infrared light-emitting diode (LED), the optical isolator, Schottky clamped logic circuits, silicon Metal Oxide Semiconductor Read Only Memory (MOS ROM), a low bulk leakage current avalanche photodetector, and fiber-optic data links.

Seven-segment display

7-segment displayseven segment displayseven-segment
Early LEDs were often used as indicator lamps, replacing small incandescent bulbs, and in seven-segment displays. The first commercial visible-wavelength LEDs were commonly used as replacements for incandescent and neon indicator lamps, and in seven-segment displays, first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as calculators, TVs, radios, telephones, as well as watches (see list of signal uses).
Seven-segment displays may use a liquid crystal display (LCD), a light-emitting diode (LED) for each segment, an electrochromic display, or other light-generating or controlling techniques such as cold cathode gas discharge (Panaplex), vacuum fluorescent (VFD), incandescent filaments (Numitron), and others.

Gallium arsenide

GaAsgallium(III) arsenidegallium-arsenide
Rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide (GaAs) and other semiconductor alloys in 1955.
Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circuits, infrared light-emitting diodes, laser diodes, solar cells and optical windows.

Nick Holonyak

Nick Holonyak, Jr.Nick Holonyak Jr.Dr. Nicholas Holonyak
The first visible-spectrum (red) LED was developed in 1962 by Nick Holonyak, Jr. while working at General Electric.
He is noted particularly for his 1962 invention of a light-emitting diode (LED) that emitted visible red light instead of infrared light; Holonyak was then working at General Electric's research laboratory in Syracuse, New York.

LED display

LED screensLEDLED screen
The first usable LED products were HP's LED display and Monsanto's LED indicator lamp, both launched in 1968.
A LED display is a flat panel display that uses an array of light-emitting diodes as pixels for a video display.

Light

visible lightvisiblelight source
A light-emitting diode (LED) is a semiconductor light source that emits light when current flows through it.
Emission can be spontaneous, as in light-emitting diodes, gas discharge lamps (such as neon lamps and neon signs, mercury-vapor lamps, etc.), and flames (light from the hot gas itself—so, for example, sodium in a gas flame emits characteristic yellow light).

M. George Craford

M. George Craford, a former graduate student of Holonyak, invented the first yellow LED and improved the brightness of red and red-orange LEDs by a factor of ten in 1972.
M. George Craford is an American electrical engineer known for his work in Light Emitting Diodes (LEDs).

Electroluminescence

electroluminescentelectroluminescent panelEL
Electroluminescence as a phenomenon was discovered in 1907 by the British experimenter H. J. Round of Marconi Labs, using a crystal of silicon carbide and a cat's-whisker detector.
Prior to recombination, electrons and holes may be separated either by doping the material to form a p-n junction (in semiconductor electroluminescent devices such as light-emitting diodes) or through excitation by impact of high-energy electrons accelerated by a strong electric field (as with the phosphors in electroluminescent displays).

Band gap

forbidden gapband-gapbandgap
The color of the light (corresponding to the energy of the photons) is determined by the energy required for electrons to cross the band gap of the semiconductor.
Other things equal, direct bandgap materials tend to be better for photovoltaics (PVs), light-emitting diodes (LEDs), and laser diodes; however, indirect bandgap materials are frequently used in PVs and LEDs when the materials have other favorable properties.

Lighting

illuminationartificial lightartificial lighting
LEDs are used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, camera flashes, lighted wallpaper, plant growing light, and medical devices.
Recessed lighting (often called "pot lights" in Canada, "can lights" or 'high hats" in the US) is popular, with fixtures mounted into the ceiling structure so as to appear flush with it. These downlights can use narrow beam spotlights, or wider-angle floodlights, both of which are bulbs having their own reflectors. There are also downlights with internal reflectors designed to accept common 'A' lamps (light bulbs) which are generally less costly than reflector lamps. Downlights can be incandescent, fluorescent, HID (high intensity discharge) or LED.

Laser diode

semiconductor laserdiode laserlaser diodes
Today, magnesium-doping of gallium nitride remains the basis for all commercial blue LEDs and laser diodes.
A laser diode, (LD), injection laser diode (ILD), or diode laser is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode's junction.

Gallium nitride

GaNgallium(III) nitridegallium nitride (GaN)
The first blue-violet LED using magnesium-doped gallium nitride was made at Stanford University in 1972 by Herb Maruska and Wally Rhines, doctoral students in materials science and engineering. In parallel, Isamu Akasaki and Hiroshi Amano in Nagoya were working on developing the important GaN deposition on sapphire substrates and the demonstration of p-type doping of GaN.
Gallium nitride () is a binary III/V direct bandgap semiconductor commonly used in light-emitting diodes since the 1990s.

Mohamed M. Atalla

Mohamed AtallaMartin Mohamed AtallaMohamed Mohamed Atalla
Hewlett-Packard (HP) was engaged in research and development (R&D) on practical LEDs between 1962 and 1968, by a research team under Howard C. Borden, Gerald P. Pighini and Mohamed M. Atalla at HP Associates and HP Labs.
His work at HP and Fairchild included further research on Schottky diodes, in addition to research on gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), indium arsenide (InAs) and light-emitting diode (LED) technologies, contributing to the development of high-frequency network analyzers, developing the first practical LED displays, and proposing LED optical readers.

Cree Inc.

CreeCree IncCree Research Inc.
In August 1989, Cree introduced the first commercially available blue LED based on the indirect bandgap semiconductor, silicon carbide (SiC).
Cree, Inc. is an American manufacturer and marketer of lighting-class LEDs, lighting products and products for power and radio frequency (RF) applications.

P–n junction

p-n junctionreverse biasjunction
On August 8, 1962, Biard and Pittman filed a patent titled "Semiconductor Radiant Diode" based on their findings, which described a zinc-diffused p–n junction LED with a spaced cathode contact to allow for efficient emission of infrared light under forward bias.
p–n junctions are elementary "building blocks" of semiconductor electronic devices such as diodes, transistors, solar cells, LEDs, and integrated circuits; they are the active sites where the electronic action of the device takes place.

Neon lamp

neonneon bulbneon lights
The first commercial visible-wavelength LEDs were commonly used as replacements for incandescent and neon indicator lamps, and in seven-segment displays, first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as calculators, TVs, radios, telephones, as well as watches (see list of signal uses).
Glow lamps found practical use as indicators in instrument panels and in many home appliances until the widespread commercialization of light-emitting diodes (LEDs) in the 1970s.

Isamu Akasaki

In parallel, Isamu Akasaki and Hiroshi Amano in Nagoya were working on developing the important GaN deposition on sapphire substrates and the demonstration of p-type doping of GaN.
Isamu Akasaki is a Japanese engineer and physicist, specializing in the field of semiconductor technology and Nobel Prize laureate, best known for inventing the bright gallium nitride (GaN) p-n junction blue LED in 1989 and subsequently the high-brightness GaN blue LED as well.

Shuji Nakamura

Nakamura, ShujiS. NakamuraShūji Nakamura
Two years later, in 1993, high-brightness blue LEDs were demonstrated by Shuji Nakamura of Nichia Corporation using a gallium nitride growth process.
Shuji Nakamura is a Japanese-born American electronic engineer and inventor specializing in the field of semiconductor technology, professor at the Materials Department of the College of Engineering, University of California, Santa Barbara (UCSB), and is regarded as the inventor of the blue LED, a major breakthrough in lighting technology.

Phosphor

phosphorsP39 phosphorP7 phosphor
Using different phosphors produces green and red light through fluorescence.
Phosphorescent materials are known for their use in radar screens and glow-in-the-dark materials, whereas fluorescent materials are common in cathode ray tube (CRT) and plasma video display screens, fluorescent lights, sensors, and white LEDs.

Light-emitting diode physics

selection of different semiconductor materials
By selection of different semiconductor materials, single-color LEDs can be made that emit light in a narrow band of wavelengths from near-infrared through the visible spectrum and into the ultraviolet range.
In light-emitting diode physics, the recombination of electrons and electron holes in a semiconductor produce light (or infrared radiation), a process called "electroluminescence".