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03/05/2011

New semiconductor

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" 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.plate heat exchanger
CLFs are still a good deal both financially and environmentally. They use about one quarter of the energy of incandescent bulbs and will last about 10 years, or 10 times as long, according to Consumer Reports tests. But Consumer Reports also found that turning a CFL on and off within less than 15 minutes, something you might do in the bathroom for instance, leads to earlier-than-expected brownouts.
Until 1968, visible and infrared LEDs were extremely costly, on the order of US $200 per unit, and so had little practical use.
The Monsanto Company was the first organization to mass-produce visible LEDs, using gallium arsenide phosphide in 1968 to produce red LED light suitable for indicators. Hewlett Packard (HP) introduced LEDs in 1968, initially using GaAsP supplied by Monsanto. The technology proved to have major uses for alphanumeric displays and was integrated into HP's early handheld calculators. In the 1970s commercially successful LED devices at under 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 Fairchild Semiconductor. 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. These methods continue to be used by LED strip light producers.
Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor.
That rapid cycling issue, plus the arrival of good LEDs in the traditional A19 bulb shape, got me rethinking my home lighting and prodded me to use different bulb types for different purposes. I'm still focused on efficiency, so I'm only using incandescent bulbs in places where the light is used in short spurts. I tend to go in and out of the attic quickly, for example, and want full brightness as soon as possible