LED-Definition

In this article, we discuss the oldest optoelectronic device, LED definition.  LED is widely used in many applications like sensor devices, display systems, logic gates, automobiles, optical communication systems. LED is made up of various semiconductor materials that support radiative light emission and higher efficiency. These semiconductor materials can be grown by various techniques in engineering physics. We also look at the applications, merits, and demerits of LED in detail.

LED definition

The LED-Light emitting diode is an optoelectronic device mainly composed of semiconductor material diodes. When the LEDs are forward biased or external voltage applied, light emission occurs. In simple words, it is used for the conversion of electrical to light energy.

LED semiconductor material

The LED is made up of semiconductor alloy materials like; 

• GaP

• GaAsP

• GaAs

• GaN

• ZnS

• ZnTe

• GaInP

The reason behind the usage of these semiconductor materials is they possess the direct bandgap. It gives the radiative light emission. It also provides high efficiency. Along with LED, these semiconductor materials are widely used in visible light, ultraviolet light, and infrared light. 

Preparation of semiconductor alloys used for LED

 The semiconductor alloys are prepared by two techniques: 

• MOCVD – Metal-Organic Chemical Vapour Deposition

• MBE – Molecular Beam Epitaxy

 The semiconductor materials are fabricated to produce various forms of LEDs. These LEDs possess the characteristics like surface and edge-emitting, resonant cavity, a double heterostructure, or white light LED.

Structural design of LED

The LED consists of three layers:

• P layer

• N layer

• Depletion region.

 The P layer has majority carriers called holes, and minority carriers called free electrons. The N layer has minority carriers called electrons and majority carriers called holes. The depletion region is the region that opposes the flow of electric current. It is the barrier found between the P and N layers.

 The efficient design of LED can be achieved by three methods:

• Minority carrier recombination

• Forward biased generation of minority carriers

• Photon transmission

Working of LED

The  PN junction has a heavily doped N layer and a very thin P layer. The external voltage is applied on both the layers of LED, and the light is emitted from the thin P layer. As we already know, the N layer is thicker than the P layer. The major carrier recombination occurs when the depletion region moves towards the thin P layer. The photon is emitted as a result of the recombination process. 

 The barrier region contains a certain voltage in it. So, we should apply an external voltage larger than that. As a result of this, the flow of electric current starts. The electric current turns the LED on. 

Colour of LED

LED colour can be varied based on the led semiconductor material used. Different colours are emitted by different semiconductor materials, as listed below.

Light emitted by the LED

Visible and invisible light is emitted from an LED. The visible LED light is used for illumination and display purposes. These are used without photosensors. The invisible LED uses photosensors for illumination—for example, photodiodes.

Merits of LED

• It consumes less energy compared to other optoelectronic devices.

• Its brightness can be easily adjusted by the current variations in the circuit. It helps in using the LED in different conditions or environments.

• It is very cost-effective, lightweight, and easily available.

• Its operation is much faster as it is very small in size.

• The emission of different colours are possible in LED

• The usage of toxic materials is avoided during manufacturing. For example, fluorescent lamps have toxic materials like mercury in them.

Demerits of LED

• The lumination is low in LED

• The power requirement is more in LEDs.

Applications of LED

We can find LEDs in most devices we use every day like computers, calculators, watches, cameras. It can be found in the laboratory instruments like microprocessors, multimeters, and burglar alarm systems. It is used in traffic signals and aviation lighting.

Conclusion

In this article, we have discussed the definition of LED. It is made up of LED semiconductor material with modern techniques. It consists of three layers used for the effective functionality of LEDs. LEDs produce light in many colours besides white. LED is produced by advanced methods and is used in many applications like illumination, optical communication, and fibre technology. The article also covered the advantages and disadvantages of LED and its applications.