The history of the light-emitting diode begins with the 1906 discovery of electroluminescence from a solid state diode by Henry Joseph Round. In 1927, Russian inventor Oleg Losev created the first LED. The first practical LED was developed in 1961 by researchers at Texas Instruments. The 1970s saw the first commercial LEDs. In the early 1990s, Shuji Nakamura, Hiroshi Amano and Isamu Akasaki invented blue LEDs that were dramatically more efficient than their predecessors, bringing a new generation of bright, energy-efficient white lighting and full-color LED displays into practical use, work that won them the 2014 Nobel Prize in Physics.
Early experiments Round, of Marconi Labs, made his discovery in 1906 while using a cat's-whisker detector and passing current through combinations of carborundum (silicon carbide) crystal. He noticed that some gave off light – the first known report of the effect of the light-emitting diode (LED).
Round published his result in 1907 in Electrical World:. Round's letter is dated 9 February 1907.
A light-emitting diode was created, in 1927, by Russian inventor Oleg Losev, English translation: that also used silicon carbide as a semiconductor. Despite having distributed his report in Soviet, German and British scientific journals, Losev's LED found no practical use for several decades, partly due to the very inefficient light-producing properties of the semiconductor used.
In 1936, Georges Destriau observed that electroluminescence could be produced when zinc sulphide (ZnS) powder is suspended in an insulator and an alternating electrical field is applied to it. In his publications, Destriau often referred to luminescence as Losev-Light. Destriau worked in the laboratories of Madame Marie Curie, also an early pioneer in the field of luminescence with research on radium.McGraw-Hill Concise Encyclopedia of Physics: electroluminescence. (n.d.) McGraw-Hill Concise Encyclopedia of Physics. (2002).
Hungarian Zoltán Bay together with György Szigeti patenting a lighting device in Hungary in 1939 based on silicon carbide, with an option on boron carbide, that emitted white, yellowish white, or greenish white depending on impurities present. Kurt Lehovec, Carl Accardo, and Edward Jamgochian explained these first LEDs in 1951 using an apparatus employing SiC crystals with a current source of a battery or a pulse generator and with a comparison to a variant, pure, crystal in 1953.
Rubin 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 antimonide (GaSb), GaAs, indium phosphide (InP), and silicon-germanium (SiGe) alloys at room temperature and at 77K. 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."
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. 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.Matzen, W. T. ed. (March 1963) "Semiconductor Single-Crystal Circuit Development", Texas Instruments Inc., Contract No. AF33(616)-6600, Rept. No ASD-TDR-63-281. 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 G.E. Labs, RCA Research Labs, IBM Research Labs, Bell Labs, and Lincoln Lab at MIT, the U.S. patent office issued the two inventors the patent for the GaAs infrared light-emitting diode (U.S. Patent 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 an 890 nm light output. In October 1963, TI announced the first commercial hemispherical LED, the SNX-110.
In the 1960s, several laboratories focused on LEDs that would emit visible light. A particularly important device was demonstrated by Nick Holonyak on October 9, 1962, while he was working for General Electric in Syracuse, New York. The device used the semiconducting alloy gallium phosphide arsenide (GaAsP). It was the first semiconductor laser to emit visible light, albeit at low temperatures. At room temperature it still functioned as a red light-emitting diode. GaAsP was the basis for the first wave of commercial LEDs emitting visible light. It was mass-produced by the Monsanto and Hewlett-Packard companies and used widely for displays in calculators and wrist watches.
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 designed the first high-brightness, high-efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths.
In the early 1990s, Shuji Nakamura, Hiroshi Amano and Isamu Akasaki invented blue light-emitting diodes that were dramatically more efficient than their predecessors, bringing a new generation of bright, energy-efficient white lighting and full-color LED displays into practical use and winning the 2014 Nobel Prize in Physics. Shuji Nakamura is credited as the researcher who invented the LEDs and his research was expanded on by Hiroshi Amano and Isamu Akasaki who solved two of the three main problems in creating blue LEDs.
Initial commercial development
Until 1968, visible and infrared LEDs were extremely costly, on the order of US$200 per unit, and so had little practical use. The first commercial visible-wavelength LEDs used GaAsP semiconductors and 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.
The Hewlett-Packard company (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 at HP Associates and HP Labs. During this time HP collaborated with Monsanto Company on developing the first usable LED products. The first usable LED products were HP's LED display and Monsanto's LED indicator lamp, both launched in 1968.
Monsanto was the first organization to mass-produce visible LEDs, using Gallium arsenide phosphide (GaAsP) in 1968 to produce red LEDs suitable for indicators. Monsanto had previously offered to supply HP with GaAsP, but HP decided to grow its own GaAsP. In February 1969, Hewlett-Packard introduced the HP Model 5082-7000 Numeric Indicator, the first LED device to use integrated circuit (integrated LED circuit) technology. It was the first intelligent LED display, and was a revolution in digital display technology, replacing the Nixie tube and becoming the basis for later LED displays.
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 (developed by Jean Hoerni,Patent number: 3025589 Retrieved May 17, 2013 ). 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 have continued to use these methods as of about 2009.
The early red LEDs were bright enough for use as indicators, but 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.
Early LEDs were packaged in metal cases similar to those of transistors, with a glass window or lens to let the light out. Modern indicator LEDs are packed in transparent molded plastic cases, tubular or rectangular in shape, and often tinted to match the device color. Infrared devices may be dyed, to block visible light. More complex packages have been adapted for efficient heat dissipation in high-power LEDs. Surface-mounted LEDs further reduce the package size. LEDs intended for use with fiber optics cables may be provided with an optical connector.
Blue LED 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."Nobel Shocker: RCA Had the First Blue LED in 1972". IEEE Spectrum. October 9, 2014,"Oregon tech CEO says Nobel Prize in Physics overlooks the actual inventors" . The Oregonian. October 16, 2014 At the time Maruska was on leave from RCA Laboratories, where he collaborated with Jacques Pankove on related work. In 1971, the year after Maruska left for Stanford, his RCA colleagues Pankove and Ed Miller demonstrated the first blue electroluminescence from zinc-doped gallium nitride, though the subsequent device Pankove and Miller built, the first actual gallium nitride light-emitting diode, emitted green light.Schubert, E. Fred (2006) Light-emitting diodes (2nd ed.), Cambridge University Press. pp. 16–17Maruska, H. (2005). "A Brief History of GaN Blue Light-Emitting Diodes". LIGHTimes Online – LED Industry News.
In 1974 the U.S. Patent Office awarded Maruska, Rhines, and Stanford professor David Stevenson a patent for their work in 1972 (U.S. Patent US3819974 A). Today, magnesium-doping of gallium nitride remains the basis for all commercial blue LEDs and laser diodes. In the early 1970s, these devices were too dim for practical use, and research into gallium nitride devices slowed.
In August 1989, Cree introduced the first commercially available blue LED, based on the indirect bandgap semiconductor, silicon carbide (SiC).Major Business and Product Milestones. Cree.com. Retrieved on March 16, 2012. SiC LEDs had very low efficiency, no more than about 0.03%, but did emit in the blue portion of the visible light spectrum.
In the late 1980s, key breakthroughs in GaN epitaxial growth and p-type doping ushered in the modern era of GaN-based optoelectronic devices. Building upon this foundation, Theodore Moustakas at Boston University patented a method for producing high-brightness blue LEDs using a new two-step process in 1991.Moustakas, Theodore D. "Highly insulating monocrystalline gallium nitride thin films" Issue date: March 18, 1991 In 2015, a US court ruled that three Taiwanese companies had infringed Moustakas's prior patent, and ordered them to pay licensing fees of not less than US$13 million.