LED: Difference between revisions

An LED (Light Emitting Diode) is a type of solid-state lighting.  In keeping with the properties of a diode, electric current can only flow one direction through an LED.  As the electrons cross from a material abundant in negative charge carriers to a material abundant in positive carriers active region, they lose a specific amount of energy, which results in photons of a particular wavelength.  Different semiconductors used in the manufacture of LEDs will result in different wavelengths (colors) of light emitted.  Currently, the brightest semiconductor materials are Aluminum Indium Gallium Phosphide (AlInGaP) for reds, oranges, ambers and yellows, and Indium Gallium Nitride (InGaN) for blues and greens.  A white LED is typically a blue LED coated in a yellow emitting phosphor (this is why flashlight LED's appear yellow when they are off), or combination of phosphors, which are excited by the blue light and produce light as a result.  When this yellow light mixes with the blue light from the LED, the combined light appears white to the human eye.