Many people believe that the LED was discovered by US researchers
working in the 1960s. In fact, Henry Round at Marconi Labs noted the
emission of light from a semiconductor diode over 100 years ago and,
independently, a forgotten Russian genius named Oleg Losev
discovered the LED.
It All Started With
Electroluminescence 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.
Read this facsimile of a paper he wrote in February 1907 to
Vladimirovich Losev independently created the first LED in the mid 1920s
his research was distributed in Russian, German and British
but no practical use was made of the discovery for several decades.
A Forgotten Figure
Much less is
known about the inventor of the LED itself. As it turns out, the
story is a tragic
one about a young and extremely talented scientist.
Discovery of Infrared Emissions
Braunstein 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
GaAs, indium phosphide (InP), and silicon-germanium (SiGe)
room temperature and at 77 kelvin.
The First Patent For The Infrared LED
In 1961, experimenters Bob Biard and Gary Pittman working at Texas Instruments, found that GaAs emitted infrared radiation when electric current was applied and received the patent for the
The Father Of LED's
practical visible-spectrum (red) LED was developed in 1962 by Nick
Holonyak Jr., while working at General Electric Company. Holonyak is
seen as the "father of the light-emitting diode".
He is a John
Bardeen Endowed Chair in Electrical and Computer Engineering and
Physics and Professor of electrical and computer engineering at the
University of Illinois at Urbana-Champaign where he has been since
Read more about him
The First Yellow LED
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.
George obtained a Ph.D. degree in physics from
the University of Illinois in 1967. He began his professional career
as a research physicist at Monsanto Chemical Company, before joining
the Hewlett Packard Company in 1979.
The first commercial LEDs
were commonly used as replacements for incandescent indicators, and
in seven-segment displays, first in expensive equipment such as
laboratory and electronics test equipment, then later in such
appliances as TVs, radios, telephones, calculators, and even
These red LEDs were bright enough only for use as
indicators, as the light output was not enough to illuminate an
Later, other colors became widely available and also
appeared in appliances and equipment. As the LED materials
technology became more advanced, the light output was increased,
while maintaining the efficiency and the reliability to an
The invention and development of the high
power white light LED has led to uses for illumination. Most LEDs
were made in the very common 5 mm T1¾ and 3 mm T1 packages, but with
increasing power output, it has become increasingly necessary to
shed excess heat in order 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.
High Brightness LED's
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. Companies such as Lumileds and Cree Inc.
have designed and marketed LEDs that operate at 1 watt and higher
making it possible for them to build a light bulb that is brighter
has the same color as an incandescent light bulb. Unfortunately
we're still waiting (as of 2009) for an LED light bulb that covers
the same area (360 degrees), is as bright, and costs about as much
as an incandescent light bulb.
LED's Used To Be Very Expensive
Up to 1968, visible
and infrared LEDs were extremely costly, on the order of US $200 per
unit, and so had little practical application.
Corporation was the first organization to mass-produce visible LEDs,
using gallium arsenide phosphide in 1968 to produce red LEDs
suitable for indicators. Hewlett Packard (HP) introduced LEDs in
1968, initially using GaAsP supplied by Monsanto. The technology
proved to have major applications for alphanumeric displays and was
integrated into HP's early handheld calculators.