A Light Emitting Diode (LED) is a semiconductor device that emits light when an electric current passes through it. The process through which an LED produces light is known as electroluminescence and is based on the behavior of semiconductors.
Here's a simplified explanation of how an LED produces light:
Semiconductor Material: LEDs are made from semiconductor materials, typically compounds of elements from groups III and V of the periodic table. Common materials include gallium arsenide (GaAs), gallium phosphide (GaP), or gallium nitride (GaN). The specific combination of materials determines the color of the emitted light.
P-N Junction: An LED consists of a p-n junction, which is formed by combining two different types of semiconductor materials: the "p-type" with an excess of positively charged holes and the "n-type" with an excess of negatively charged electrons. The junction between these two regions is where light emission occurs.
Forward Bias: When a forward voltage is applied to the LED (connecting the positive side of a power supply to the p-side and the negative side to the n-side), electrons from the n-region and holes from the p-region start to flow toward the junction.
Recombination: As the electrons and holes approach the p-n junction, they combine or recombine. During this recombination process, the electrons lose energy, which is released in the form of photons, i.e., light.
Emission of Light: The photons produced by the recombination process are of a specific wavelength, corresponding to the energy bandgap of the semiconductor material. This determines the color of the emitted light, which can range from ultraviolet to visible colors and even infrared, depending on the materials used.
Quantum Wells (Optional): Some advanced LEDs use quantum wells – thin layers of different semiconductor materials within the p-n junction – to further control and improve the efficiency of light emission.
The unique property of the semiconductor materials and the recombination process in the p-n junction allow LEDs to produce light efficiently and with lower power consumption compared to traditional incandescent or fluorescent light sources. LEDs are commonly used in various applications, such as lighting, displays, indicators, and electronic devices.