How different L.E.Ds Produce Different colours ?

How different L.E.Ds Produce Different colours ?

Thanks

it depends upon material used while manufacturing

some LEDs r actually which r transparent depend upon material like i think germinium arsenide

and low acst LED depends on plastic body

i hope u know about solid state devices..why silicon dont emit light?? why germanium dont emit light??
its all bcoz of their bandgap energy level. semiconductors can be grouped in two ways
(i)direct bandgap semiconductor and
(ii)indirect bandgap semiconductor

in direct bandgap semiconductor lower lever of conduction band and higher level of valence band fall in the same level, its not in the case of indirect bandgap.
in indirect bandgap semiconductor electrons from conduction band fall to a intermidiate state and from there to valence band. Energy will be released during this process in the form of heat.
let me come to ur question...let us take a light emitting semiconductor GaAs which is a direct bandgap semiconductor, when electrons fall from conduction band to valence band energy is released which is equal to
E=hf
where f - frequency
h-planks constant
if this frequency is in the range of visible light, then the semiconductor can emit light, the color of the light depends on the frequency which in turn depends on the bandgap. this is not in the case of silicon and germanium..so they cant emit light..
Human will not leave anything untouched...if we want we can make any semiconductor to emit light of any color by altering its bandgap..

contact me if u have any doubt..

Conventional LEDs are made from a variety of inorganic semiconductor materials, producing the following 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
* gallium arsenide phosphide (GaAsP) - red, orange-red, orange, and yellow
* gallium phosphide (GaP) - red, yellow and green
* gallium nitride (GaN) - green, pure green (or emerald green), and blue
* indium gallium nitride (InGaN) - near ultraviolet, bluish-green and blue
* silicon carbide (SiC) as substrate - blue
* silicon (Si) as substrate - blue (under development)
* sapphire (Al2O3) as substrate - blue
* zinc selenide (ZnSe) - blue
* diamond (C) - ultraviolet
* aluminum nitride (AlN), aluminum gallium nitride (AlGaN) - near to far ultraviolet