Short Answer

Intrinsic semiconductors are pure semiconductor materials without any impurities. Their electrical conductivity depends only on temperature. Examples include pure silicon and germanium.

Extrinsic semiconductors are formed by adding small amounts of impurities to intrinsic semiconductors. This process is called doping. It increases the conductivity of the material and creates two types: n-type and p-type semiconductors.

Detailed Explanation:

Intrinsic and extrinsic semiconductors

Intrinsic semiconductors

Intrinsic semiconductors are pure forms of semiconductor materials with no added impurities. In these materials, the number of free electrons is equal to the number of holes.

At very low temperature, intrinsic semiconductors behave like insulators because there are no free charge carriers. However, as temperature increases, some electrons gain enough energy to break their bonds and move to the conduction band.

When an electron leaves its position, it creates a hole in the valence band. Both electrons and holes act as charge carriers and help in conduction. Since their numbers are equal, the conductivity is limited.

Examples of intrinsic semiconductors include pure silicon and pure germanium. These materials are not very useful in practical electronic devices because their conductivity is low and difficult to control.

The conductivity of intrinsic semiconductors mainly depends on temperature. As temperature increases, more electrons move to the conduction band, increasing conductivity.

Extrinsic semiconductors

Extrinsic semiconductors are formed by adding impurities to intrinsic semiconductors. This process is called doping. The added impurities increase the number of charge carriers and improve conductivity.

There are two types of extrinsic semiconductors:

N-type semiconductor is formed by adding pentavalent impurities such as phosphorus or arsenic. These atoms have five valence electrons. Four electrons form bonds with the semiconductor atoms, and the fifth electron becomes free. This increases the number of free electrons, making electrons the majority charge carriers.

P-type semiconductor is formed by adding trivalent impurities such as boron or aluminum. These atoms have three valence electrons. When they form bonds, one bond remains incomplete, creating a hole. This increases the number of holes, making holes the majority charge carriers.

In extrinsic semiconductors, conductivity is much higher compared to intrinsic semiconductors. Also, conductivity can be controlled by selecting the type and amount of impurity.

Key differences

Intrinsic semiconductors are pure and have equal numbers of electrons and holes, while extrinsic semiconductors contain impurities and have unequal numbers of charge carriers.

Intrinsic semiconductors have low conductivity, while extrinsic semiconductors have high conductivity due to doping.

In intrinsic semiconductors, temperature mainly controls conductivity. In extrinsic semiconductors, both doping and temperature affect conductivity.

Extrinsic semiconductors are widely used in electronic devices because they provide better control over electrical properties.

Importance in electronics

Intrinsic and extrinsic semiconductors are very important in electronics and communication engineering. Most electronic devices use extrinsic semiconductors because of their higher and controllable conductivity.

Devices like diodes, transistors, and integrated circuits are made using n-type and p-type semiconductors. These devices are the basic building blocks of modern electronic systems.

Understanding the difference between intrinsic and extrinsic semiconductors helps in designing and improving electronic circuits.

Conclusion

Intrinsic semiconductors are pure materials with limited conductivity, while extrinsic semiconductors are doped materials with improved and controlled conductivity. Both types are important, but extrinsic semiconductors are more useful in practical electronic applications.