A light-emitting diode (LED) is a semiconductor device that emits light when an electric current is passed through it. The construction of an LED consists of several layers of semiconductor materials, including a p-type semiconductor layer and an n-type semiconductor layer. The p-type layer is made of a semiconductor material doped with a small amount of impurities, such as boron, which creates a surplus of holes (positive charges) in the material. The n-type layer is made of a semiconductor material doped with impurities such as phosphorus, which creates a surplus of electrons (negative charges) in the material.
When an electric current is applied to the LED, it flows through the p-type layer and the n-type layer, creating a flow of holes and electrons. The holes and electrons then recombine in the junction between the p-type layer and the n-type layer, releasing energy in the form of light. This light is emitted from the LED as a result of the recombination of the holes and electrons. The color of the light emitted by an LED depends on the materials used to make the semiconductor layers, as well as the energy band gap of the semiconductor material. The higher the energy band gap, the more energy is released when the holes and electrons recombine, resulting in a higher-frequency, and therefore a different color, of light.
In summary, an LED is a semiconductor device that emits light when an electric current is passed through it. The construction of an LED consists of several layers of semiconductor materials, p-type semiconductor layer and an n-type semiconductor layer, and a junction between them. When an electric current is applied to the LED, it causes recombination of holes and electrons in the junction, releasing energy in the form of light. The color of the light emitted by an LED depends on the materials used to make the semiconductor layers, as well as the energy band gap of the semiconductor material.