Light Emitting Diode Colours
• So how does a light emitting diode get its colour. Unlike normal signal
diodes which are made for detection or power rectification, and
which are made from either Germanium or Silicon semiconductor
materials, Light Emitting Diodes are made from exotic semiconductor
compounds such as Gallium Arsenide (GaAs), Gallium Phosphide
(GaP), Gallium Arsenide Phosphide (GaAsP), Silicon Carbide (SiC) or
Gallium Indium Nitride (GaInN) all mixed together at different ratios
to produce a distinct wavelength of colour.
Light Emitting Diode The “Light Emitting Diode” or LED as it is more commonly called, is basically just a specialised type of diode as they have very similar electrical characteristics to a PN junction diode. This means that an LED will pass current in its forward direction but block the flow of current in the reverse direction. • Light emitting diodes are made from a very thin layer of fairly heavily doped semiconductor material and depending on the semiconductor material used and the amount of doping, when forward biased an LED will emit a coloured light at a particular spectral wavelength. • When the diode is forward biased, electrons from the semiconductors conduction band recombine with holes from the valence band releasing sufficient energy to produce photons which emit a monochromatic (single colour) of light. Because of this thin layer a reasonable number of these photons can leave the junction and radiate away producing a coloured light output. • Also, nearly al...
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