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LEDs (light emitting diodes) are solid-state semiconductor devices that can convert electrical energy directly into light. The heart of a led is a semiconductor chip of which one side is attached on the top of an anvil that is the negative power lead, and the other side is connected with a whisker to a positive power lead. it is the most important part of the LED, and it is entirely encapsulated in an epoxy resin enclosure.
A semiconductor chip consists of two parts, one is called P- type semiconductor where holes dominate the region, and the other part is N-type semiconductor where is dominate by electrons. When they are sandwiched together, there is a PN junction in between. And when an electric current is applied to the chip through the lead, electrons are pushed across the junction into the P-region, there, electrons and holes meet and recombine, and then release energy in the form of photons of light. That is why LED can shine. And the wavelength of the light, therefore its color, depends on the materials forming the PN junction, which is, the materials used to make the LED chip.
Generally, LED chips are made from gallium-based crystals that contain one or more additional materials such as phosphor to produce a distinct color. |
