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LEDs

LEDs. Kang Bae Material Science MEEN 3344. What is LED. LED stands for Light Emitting Diode. LED is a semiconductor device that produces infrared lights when electric current is applied to the device This process is also called Electroluminescense. HISTORY OF LED.

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LEDs

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  1. LEDs Kang Bae Material Science MEEN 3344

  2. What is LED • LED stands for Light Emitting Diode. • LED is a semiconductor device that produces infrared lights when electric current is applied to the device • This process is also called Electroluminescense

  3. HISTORY OF LED • Radio Corporation of America first reported on infrared emission from gallium arsenide in 1955. • Texas Instrument found Gallium Arsenide emits infrared lights when electric current were applied 1961. • GE developed the first working LED in 1962.

  4. How LED works • A LED is a semiconductor diode that consists of a chip of semiconducting material that creates a p-n junction. • P-N junction is where current flows and it flows from the p-side to the n-side • Charge-carriers - electrons and electron holes - flow into the junction • releases energy in the form of a photon. • The wavelength of the light emitted distinguishes LED’s color • Examples of colors • aluminum gallium arsenide (AlGaAs) - red and infrared • aluminum gallium phosphide (AlGaP) - green • aluminum gallium indium phosphide (AlGaInP) - high-brightness orange-red, orange, yellow, and green • diamond (C) - ultraviolet

  5. Uses of LED • flash lights. • LED Display • Bicycle lights • Traffic signs and signals • Mouse for computers • Cars (Lexus tailamp)

  6. Advantages and Disadvantage • Lasts longer than incandescent lights • Extremely durable and less heat • Lights up in microseconds • High ambient temperature cause overheat. • More efficient, lower power usage than incandescent lights.

  7. References • Whatis June 18 2001, Nov 9 2006 http://whatis.techtarget.com/definition/0,,sid9_gci213613,00.html • Wikipedia Nov 9 2006, Nov 9 2006 http://en.wikipedia.org/wiki/LED_%28Light-emitting_diode%29#Physical_function

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