An LED or Light Emitting Diode is an optoelectronic device that can emit light when properly polarized. Early light-emitting diodes used to emit a fairly low intensity beam of light, but modern ones compensate for this delay with adequate illumination or light output. The light emitted by modern LEDs is at many wavelengths and therefore offers a wide range of colors for us to choose from. The main advantages of LEDs are their limited power consumption and their very high efficiency. They are quite robust, rugged and strong enough to withstand the mechanical impacts given to them, have a very fast switching response and are very compact.
A light emitting diode is almost similar in construction to a pn diode; The light-emitting diode is made of a semiconductor material such as silicon or germanium, which is doped with p-type and n-type impurities to obtain a pn array. The LED usually consists of the following parts, an epoxy lens or casing to cover the semiconductor material, wire junctions, reflective cavity, semiconductor die, and anvil post, which is also known as lead frame.
When a potential is applied to this device, a current flows through the resulting junction due to the recombination of the holes and electrons, the recombination resulting in the release of energy in the form of photons of light.
LED production actually began with red and infrared devices, which contained gallium arsenide. Now many ranges of colors are available when looking for a particular type of LED. Advances in materials science and physics have led to the manufacture of LEDs with shorter wavelengths than ever before.
Light-emitting diodes are built on an n-type substrate with an electrode attached to the p-type layer deposited on the surface. The sapphire substrate is in common use in modern light-emitting diodes. Most materials for making light-emitting diodes have a high refractive index. A lot of light is reflected at the air surface interface of the material.
The usual red LEDs that most of us come across are made of gallium arsenide phosphide, orange ones can also be made of the same material, zinc selenide is used for the manufacture of blue LEDs, in this way many chemical compounds form the raw materials for the manufacture of LED’s of different colors.
The next time you use an LED, now you’ll know what they’re made of!