LED Light Bulb Guide - Light Generation in LEDs
The light from an LED is produced by exciting a semiconductor crystal electrically. In the crystal, there exist two areas – an are with a surplus of electrons (n-conducting) and an area with a deficit of electrons (p-conducting).
Between these two areas exists a transitional area, called the PN-transition or depeletion layer. It is in this area that the light is produced by electrons recombining with atoms lacking an electron. This occurs when a current is applied across the crystal.
The emission spectrum of semiconductors is narrow and as such, the materials used in the semiconductor is important in determining the wavelength of light produced and the colour of the LED.
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