1. Kang Bae Material Science MEEN 3344
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 , Nov
Wikipedia Nov , Nov