Discoveries and early devices
Green electroluminescence from a point contact on a crystal of
's original experiment from 1907.
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
 Russian inventor
Oleg Losev reported creation of the first LED in 1927.
 His research was distributed in Soviet, German and British scientific journals, but no practical use was made of the discovery for several decades.
Kurt Lehovec, Carl Accardo, and Edward Jamgochian explained these first light-emitting diodes in 1951 using an apparatus employing
SiC crystals with a current source of battery or pulse generator and with a comparison to a variant, pure, crystal in 1953.
 of the
Radio Corporation of America reported on infrared emission from
gallium arsenide (GaAs) and other semiconductor alloys in 1955.
 Braunstein observed infrared emission generated by simple diode structures using
gallium antimonide (GaSb), GaAs,
indium phosphide (InP), and
silicon-germanium (SiGe) alloys at room temperature and at 77 Kelvin.
In 1957, Braunstein further demonstrated that the rudimentary devices could be used for non-radio communication across a short distance. As noted by Kroemer
 Braunstein "…had set up a simple optical communications link: Music emerging from a record player was used via suitable electronics to modulate the forward current of a GaAs diode. The emitted light was detected by a PbS diode some distance away. This signal was fed into an audio amplifier and played back by a loudspeaker. Intercepting the beam stopped the music. We had a great deal of fun playing with this setup." This setup presaged the use of LEDs for optical communication applications.
A Texas Instruments SNX-100 GaAs LED contained in a TO-18 transistor metal case.
In September 1961, while working at
Texas Instruments in
James R. Biard and Gary Pittman discovered
near-infrared (900 nm) light emission from a
tunnel diode they had constructed on a GaAs substrate.
 By October 1961, they had demonstrated efficient light emission and signal coupling between a GaAs p-n junction light emitter and an electrically-isolated semiconductor photodetector.
 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. After establishing the priority of their work based on engineering notebooks predating submissions from
RCA Research Labs,
IBM Research Labs,
Bell Labs, and
Lincoln Lab at
US3293513), the first practical LED.
 Immediately after filing the patent,
Texas Instruments (TI) began a project to manufacture infrared diodes. In October 1962, TI announced the first commercial LED product (the SNX-100), which employed a pure GaAs crystal to emit a 890 nm light output.
 In October 1963, TI announced the first commercial hemispherical LED, the SNX-110.
The first visible-spectrum (red) LED was developed in 1962 by
Nick Holonyak, Jr. while working at
General Electric. Holonyak first reported his LED in the journal Applied Physics Letters on December 1, 1962.
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.
 In 1976, T. P. Pearsall created the first high-brightness, high-efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths.
Initial commercial development
The first commercial LEDs were commonly used as replacements for
neon indicator lamps, and in
 first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, as well as watches (see list of
signal uses). Until 1968, visible and infrared LEDs were extremely costly, in the order of
US$200 per unit, and so had little practical use.
Monsanto Company was the first organization to mass-produce visible LEDs, using gallium arsenide phosphide (GaAsP) in 1968 to produce red LEDs suitable for indicators.
Hewlett-Packard (HP) introduced LEDs in 1968, initially using GaAsP supplied by Monsanto. These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area. Readouts in calculators were so small that plastic lenses were built over each digit to make them legible. Later, other colors became widely available and appeared in appliances and equipment. In the 1970s commercially successful LED devices at less than five cents each were produced by Fairchild Optoelectronics. These devices employed compound semiconductor chips fabricated with the
planar process invented by Dr. Jean Hoerni at
 The combination of planar processing for chip fabrication and innovative packaging methods enabled the team at Fairchild led by optoelectronics pioneer Thomas Brandt to achieve the needed cost reductions.
 LED producers continue to use these methods.
LED display of a
scientific calculator (ca. 1978), which uses plastic lenses to increase the visible digit size
Most LEDs were made in the very common 5 mm T1¾ and 3 mm T1 packages, but with rising power output, it has grown increasingly necessary to shed excess heat to maintain reliability,
 so more complex packages have been adapted for efficient heat dissipation. Packages for state-of-the-art
high-power LEDs bear little resemblance to early LEDs.
Blue LEDs were first developed by Herbert Paul Maruska at RCA in 1972 using gallium nitride (GaN) on a sapphire substrate.
 SiC-types were first commercially sold in the
United States by Cree in 1989.
 However, neither of these initial blue LEDs were very bright.
The first high-brightness blue LED was demonstrated by
Shuji Nakamura of
Nichia Corporation in 1994 and was based on
 In parallel,
Isamu Akasaki and
Hiroshi Amano in
Nagoya were working on developing the important
GaN nucleation on sapphire substrates and the demonstration of
p-type doping of GaN. Nakamura, Akasaki, and Amano were awarded the 2014
Nobel prize in physics for their work.
 In 1995,
Alberto Barbieri at the
Cardiff University Laboratory (GB) investigated the efficiency and reliability of high-brightness LEDs and demonstrated a "transparent contact" LED using
indium tin oxide (ITO) on (AlGaInP/GaAs).
 and 2002,
 processes for growing
gallium nitride (GaN) LEDs on
silicon were successfully demonstrated. In January 2012,
Osram demonstrated high-power InGaN LEDs grown on silicon substrates commercially.
White LEDs and the illumination breakthrough
The attainment of high efficiency in blue LEDs was quickly followed by the development of the first
white LED. In this device a Y
12:Ce (known as "
YAG") phosphor coating on the emitter absorbs some of the blue emission and produces yellow light through
fluorescence. The combination of that yellow with remaining blue light appears white to the eye. However, using different
phosphors (fluorescent materials) it also became possible to instead produce green and red light through fluorescence. The resulting mixture of red, green and blue is not only perceived by humans as white light but is superior for illumination in terms of
color rendering, whereas one cannot appreciate the color of red or green objects illuminated only by the yellow (and remaining blue) wavelengths from the YAG phosphor.
, showing improvement in light output per LED over time, with a logarithmic scale on the vertical axis
The first white LEDs were expensive and inefficient. However, the light output of LEDs has increased
exponentially, with a doubling occurring approximately every 36 months since the 1960s (similar to
Moore's law). This trend is generally attributed to the parallel development of other semiconductor technologies and advances in optics and
materials science and has been called
Haitz's law after Dr. Roland Haitz.
Light output and efficiency of blue and near-ultraviolet LEDs rose as the cost of reliable devices fell. This led to relatively high-power white-light LEDs for illumination, which are replacing incandescent and fluorescent lighting.
Experimental white LEDs have been demonstrated to produce over 300 lumens per watt of electricity; some can last up to 100,000 hours.
 Compared to incandescent bulbs, this is not only a huge increase in electrical efficiency but – over time – a similar or lower cost per bulb.