What chemical is in LED?

Light Emitting Diodes (LEDs) do not contain a single "chemical" but rather utilize various semiconductor compounds specifically chosen for their ability to emit light when an electric current passes through them. These compounds are at the core of how an LED functions, determining its color and efficiency.

The Core Components: Semiconductor Compounds

The light-emitting properties of an LED depend on the specific semiconductor materials used in its active layer. These materials are precisely engineered compounds that fall under the category of III-V semiconductors, named for the groups of elements in the periodic table from which they are formed (e.g., Gallium from Group III and Nitrogen from Group V).

Here are the key semiconductor compounds commonly used in the production of LEDs:

• Gallium nitride (GaN): A fundamental material for blue, green, and ultraviolet (UV) LEDs, and a cornerstone for white LEDs (which often combine blue LEDs with a yellow phosphor).
• Aluminium gallium nitride (AlGaN): Primarily used in UV LEDs, but also plays a role in blue and green light emission.
• Indium gallium nitride (InGaN): Essential for producing blue, green, and the blue component in most white LEDs. The ratio of indium to gallium can be adjusted to tune the emitted color.
• Aluminium indium gallium phosphide (AlInGaP): Widely used for producing red, orange, and yellow LEDs.
• Gallium arsenide (GaAs): Commonly found in infrared (IR) LEDs, which are used in remote controls and sensors.
• Aluminium gallium arsenide (AlGaAs): Also used for red and infrared (IR) LEDs, providing efficient light emission in these spectral ranges.

How Different Compounds Result in Different Colors

The color of the light emitted by an LED is determined by the band gap energy of the semiconductor material. When electrons recombine with "holes" within the semiconductor, they release energy in the form of photons (light particles). The energy of these photons, and thus the color of the light, directly corresponds to the band gap energy. Different semiconductor compounds have different band gap energies, allowing manufacturers to create LEDs that emit light across the entire visible spectrum, as well as in the infrared and ultraviolet ranges.

The table below summarizes some of these key compounds and their typical light output:

These sophisticated semiconductor materials are precisely layered and structured to create the p-n junction that is the fundamental light-emitting part of an LED. The choice of material is crucial for the LED's performance, efficiency, and the specific application it is designed for.