Types of Semiconductor

Before starting with the topic, let’s first understand the Basics of semiconductors. Semiconductors are materials that have their electric conductivity between conductors and insulators. The properties and conductivity of an intrinsic Semiconductor (pure semiconductor) can be altered by adding impurities; this process of adding impurities into a semiconductor is known as doping. Most common semiconductors can be compounds such as arsenide and gallium or pure elements like germanium and silicon.

Types of semiconductors

Semiconductors are divided into two categories: intrinsic semiconductors and extrinsic semiconductors. So, here in this topic, we will briefly study intrinsic semiconductors, their making, and their uses. We will also cover the significant difference between intrinsic and extrinsic semiconductors. 

Semiconductors that are pure and impurities-free are known as intrinsic semiconductors. In this semiconductor category, no. of electrons are equal to the no. of holes.

What is an Intrinsic Semiconductor?

Intrinsic semiconductors, also referred to as pure or undoped, are flawless crystals free of other elements’ flaws and impurities.   All semiconductor materials, including those doped with other components, have intrinsic features, with the doping components introducing other desired qualities.

Intrinsic means inherent and natural, and the intrinsic semiconductors show the bulk features of semiconductor substances themselves, not the impurities and dopants. As silicon and germanium are elemental semiconductors, they are most widely used as intrinsic semiconductors. They were among the first semiconductors to be widely researched and utilised. Semiconductors’ distinctive features are founded on their electrical structure. The electrical structure, which determines semiconductors’ essential properties, is one of the mechanisms that distinguish semiconductors as a distinct kind of material.

What is an Extrinsic Semiconductor

The conductivity of the semiconductors can be improved with the help of a small number of suitable atoms known as the impurity. The process that involves adding impurities to the pure semiconductor is called doping. Generally, one atom in 107 will be replaced by a dopant atom in a doped semiconductor.

An extrinsic Semiconductor is divided into two types:

• N-type Semiconductor.
• P-type Semiconductor.

Properties N-type semiconductor

• It mainly occurs due to elections
• Completely neutral
• I = Ie and ne >> nh
• Majority- electrons and minority – holes.

When a pure semiconductor (Si & Ge) is doped in the pentavalent impurity (Sb, As, Bi, P), you will notice that four electrons out of five valence bonds will create a bond with the four electrons of Si and Ge. 

The fifth electron of the dopant will be free. In that case, an impure atom will donate one free electron for the conduction in the lattice is known as Donar.

Then the no. of electrons will increase with the addition of an impurity. Then the negative charge carrier will increase. Hence this is called an N-type semiconductor. Crystal will always act neutral, but the donor atom will automatically become an immobile ion. As conduction occurs to free many electrons, electrons found in the N-type semiconductor have majority carriers, and the holes are the minority carriers.

Properties of P-type semiconductors

• It mainly occurs due to holes.
• Completely neutral.
•  I = Ih and nh >> ne
• Majority – holes, and minority – Electrons.

Whenever a pure semiconductor is doped with the trivalent impurity (B, Ge, Al, In), then three valence electrons of the impurity bonds make a bond with the four valence electrons of the semiconductor.

In this case, the electron will be absent from the impurity. These impurity atoms, now ready to accept bonded electrons, are known as acceptors. With the increase of impurity, the hole will also increase; hence it is called the P-type semiconductor.

Difference Between Intrinsic Semiconductors And Extrinsic Semiconductors?

Conclusion

Semiconductors are devices that have conduction between a conductor and insulators and are used in everyday life in many devices like transistors, zener diodes, solar panels, switches, electric circuits, etc. Semiconductors are divided into two types, intrinsic semiconductors, and extrinsic semiconductors. Intrinsic semiconductors are pure semiconductors, and these are substances without the presence of any impurity or doping. Extrinsic semiconductors are prepared by adding a sufficient amount of impurity.