Light emitting diode (LED) is a semiconductor device which emit light when current flow through it. Electron in the semiconductor recombines with electron holes and as a result energy release in the form of photon. The color of the light depends upon the energy required for electron to cross the band gap of the semiconductor.
Light is produced within the solid semiconductor device therefore light emitting diode is describing as solid state device. The term solid state LED include also Organic LEDs(OLEDs) which distinguished this lighting technology from the other lighting sources that are used heated filament such as incandescent light and tungsten halogen lamp or gas discharge light (flu orescent light)
Working of LED
When the forward biased is applied on the P-N junction of the diode ,minority carrier electrons are injected into the p-region and corresponding minority carrier electrons are injected into the n-region.photon emission occur due to the electron –hole recombination in the p-region
Electron energy transitions across the energy gap which is called radioactive recombination, produce photons (i.e., light), while shunt energy transitions which is called non-radioactive recombination, produce phonons (i.e., heat).
In the semiconductor material of LED ,electron and holes are contain within the energy band. Emission of photon or light mainly depend upon the separation of the band i-e energy gap. The energy of photon determine the wavelength of the light which is emitted by light emitting diode and hence its color of lighs.Different semiconductor material which have different band gaps produced different color of light.
It consist compound semiconductor material which are made up of element from a group III and V of the periodic table and these are know as III-V materials. Example of III-V material which is extensively used in LED are Gallium arsenide (GaAs) and gallium phosphate (GaP).The LED color development is based upon the gallium nitride (GaN) because until mid- 90s Led has limited color ranges.
The material which us used in Light emitting diode manufacturing are given below.
- Indium Gallium Nitride (InGaN); Blue ,green and ultraviolet light –Brightness LED
- Gallum Phosphate (GaP); Yellow and Green LEDs.
- Aluminum Gallium Arsenide (AlGaAs) ;Red and infrared LEDs.
- Aluminium Gallium indium phosphate (AlGaInP) ;Yellow ,orange and red high-brightness LEDs
Uses application and uses are seen in the following devices mainly
- TV backlighting
- Smartphone backlighting
- LED display
- Automotive lighting
- Dimming of Light
- It is use in automation of various circuits
- CREE –USA
- Nichia –Japan
- Toyoda Gosei-Japan
- OSRAM –Germany
- Lumileds-San Jose
- Seoul Semconductor-South Korea
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