An LED, or Light-Emitting Diode, is a semiconductor device that emits light when an electric current passes through it. The operation of an LED is based on a phenomenon called electroluminescence. Here's a step-by-step explanation of how an LED works:
Semiconductor Material: LEDs are made from semiconductor materials, which are materials that have electrical properties between those of conductors and insulators. The most commonly used semiconductor material for LEDs is Gallium Arsenide (GaAs), but other compounds like Gallium Nitride (GaN) and Indium Gallium Nitride (InGaN) are also used for different colors of light emission.
P-N Junction: The LED is constructed with a P-N junction, which is a boundary between two different types of semiconductor materials: P-type and N-type. The P-type semiconductor has a deficiency of electrons (positive charge carriers), while the N-type semiconductor has an excess of electrons (negative charge carriers).
Electron and Hole Injection: When a forward voltage is applied to the LED (connecting the positive side to the P-type region and the negative side to the N-type region), electrons from the N-type region and holes (positive charge carriers) from the P-type region are pushed toward the P-N junction.
Recombination: At the P-N junction, the electrons and holes recombine. When an electron recombines with a hole, it releases energy in the form of a photon (a particle of light). The energy level of this photon determines the color of the light emitted.
Light Emission: The photons generated by recombination are released in a process called spontaneous emission. These photons create light, which escapes from the surface of the LED.
Reflective Cavity (Optional): Some LEDs have a reflective cavity surrounding the semiconductor material to help guide the emitted photons out of the LED more efficiently, increasing the brightness and directing the light in a specific direction.
Continuous Process: As long as the forward voltage is applied and the P-N junction remains operational, the LED will continue to emit light through the recombination of electrons and holes.
Advantages of LEDs include their high energy efficiency, long lifespan, and compact size, making them suitable for a wide range of applications, such as lighting, displays, indicators, and electronic devices. Different semiconductor materials and doping techniques are used to create LEDs with various colors, ranging from infrared and visible light (red, green, blue, etc.) to ultraviolet light.