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The History Of LEDs

Began In The Early 1900's


 

 

Discoveries and early devices

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 H.J. Round

 

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

Electrical World Magazine HERE...

 

 


 

Oleg Vladimirovich Losev

Russian Oleg Vladimirovich Losev independently created the first LED in the mid 1920s his research was distributed in Russian, German and British scientific journals, 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.

Read more about him HERE...

 


 

Discovery of Infrared Emissions

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 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 infrared LED.

 

 

 

The Father Of LED's

The first 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 1993.

Read more about him HERE...

 

 

 

 


 

Further Advancements

 

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.

 

 

 

Practical Uses

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 watches.

These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area.

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 acceptable level.

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 T1 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.

The Monsanto 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.

 

 

The TI-30 Changed Everything

Here is a picture of the Texas Instruments TI-30 hand held calculator which was introduced in 1976 with an MSRP of $24.95. This was much less than the retail prices of other scientific calculators of the era; for example, Hewlett-Packard's cheapest scientific at the time was still well over $100. It sold for less than the cost of a professional grade slide rule, which became rapidly obsolete. The low-priced TI-30 made scientific calculators far more available than before, for example to the typical high school student. The TI-30 may be the best-selling calculator ever, with an estimated 15 million manufactured during its lifespan from 1976-1983.

 

 

I actually purchased a TI-30 way back in 1979 when I started electronics classes in college. I remember the price for a brand new one was right about $25. Not bad for 30+ years ago.

 


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