What are LEDs made of?

LEDs are made of thin layers of semiconductor material; one layer will have an abundance of electrons, the next layer will have a lack of electrons.  These differences cause the electrons to move from one layer to the other generating light.  Manufacturers are now making these layers as thin as .5 micron or less (1 micron = 1 ten-thousandth of an inch).

Impurities within the semiconductors are used to make the needed electron density.  A semiconductor is a thin material that conducts electricity only when there is a high density of impurities in it.  This piece of semiconductor is a single uniform crystal, and the impurities are introduced later during the manufacturing process.  The semiconductors used for the making of a LED are Gallium Arsenide (GaAs), Gallium Phosphide (GaP),  Gallium Arsenide Phosphide (GaAsP); Indium Gallium Nitrogen (InGaN).  These different materials and impurities give the different colors of light from the LED.