Semiconductor Material | Types, Classification, Application

By Mohit Uniyal|Updated : May 23rd, 2022

Semiconductor material plays a vital role in the field of electronics. In electronic devices like diodes & transistors (BJT, JFET, MOSFET) and even in the IC technology, we are using semiconductor materials. So, every student of the electronics branch should know about these materials and among which, the most commonly used semiconductor material is also.  

We can classify the materials into three categories based on the conductivity/energy bandgap. These are Conductors, Semiconductors, and Insulators. In this article, get an overview of Semiconductor material. In addition to that, you will get to know the types of semiconductor materials available and the examples for each type.

Table of Content

Which is the Semiconductor Material?

A material is said to be a semiconductor material if its conductivity is greater than that of an insulator and less than that of a conductor. That means the conductivity of the semiconductor lies between that of the insulator and the conductor. We can define the semiconductor material based on the energy band gap also. 

The energy band gap is nothing but the difference between the lowest level of the conduction band and the highest level of the valence band. A material is said to be a semiconductor material if its energy bandgap is greater than that of a conductor and less than that of an insulator. That means the energy band gap of semiconductors lies between that of conductor and insulator. You can easily understand this one from the following diagram.

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Types of Semiconductor Material

Now, you are going to know how many types of semiconductor materials are available. We can classify the semiconductors mainly into two types based on the level of purity. Now, let’s discuss the following two types of semiconductors one by one.

  • Intrinsic Semiconductor
  • Extrinsic Semiconductor

Intrinsic Semiconductor

Intrinsic semiconductors are also called undoped semiconductors since there are no impurities. In intrinsic semiconductors, the number of electrons and holes are the same. Due to this, the conductivity is poor in this semiconductor. 

Silicon (Si) and Germanium (Ge) are examples of intrinsic semiconductors. The 4A group elements have the number of valence electrons as 4. If the total number of valence electrons is 8, then the crystal will become stable. By using covalent bonds, each Silicon (Si) atom can share one electron with four other Silicon (Si) atoms. The Silicon (Si) crystal lattice structure is shown in the below figure.

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Extrinsic Semiconductor

If we add the impurities to the intrinsic semiconductor for improving the conductivity, then that material is called an extrinsic semiconductor. The process of adding impurities to the intrinsic semiconductor is known as doping. Due to doping, the number of electrons and holes will differ in this material. 

Electrons are called negative charge carriers whereas holes are called positive charge carriers. The absence of electrons is nothing but holes. We can classify these semiconductors into the following two types based on most charge carriers.

  • n-type Semiconductor: By doping 5A group elements (N, P, As, Sb, Bi) to the intrinsic semiconductor, then electrons will become majority charge carriers. Hence, this material is called an n-type semiconductor. The following figure illustrates the doping of Phosphorus to Silicon (Si) lattice.
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  • p-type Semiconductor: By doping 3A group elements (B, Al, Ga, In, Tl) to the intrinsic semiconductor, the holes will become majority charge carriers. Hence, this material is called a p-type semiconductor. The following figure illustrates the doping of Boron to Silicon (Si) lattice.
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Applications of Semiconductor Materials

In most electronic devices and in Integrated Circuits, we use semiconductor materials. Among these, the most commonly used semiconductor material is silicon (Si). For optical devices and very high-speed devices, we use semiconductors like Gallium Arsenide (GaAs) and related compounds. 

If we use semiconductor material in an electronic device, then it is known as a semiconductor device. Examples of semiconductor devices are Diodes (p-n junction, Zener, Tunnel, Varactor, LED, Laser & photodiodes), Transistors (BJT, JFET & MOSFET) and Integrated Circuits (Analog ICs & Digital ICs). 

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FAQs on Semiconductor Material

  • The material, which has both conductivity and energy bandgap as moderate when compared to conductors & insulators, is known as a semiconductor material. There are two types of semiconductors. Those are intrinsic semiconductors and extrinsic semiconductors. These are classified based on the level of purity.

  • When we do the doping of a 5A group element with Silicon (Si) or Germanium (Ge), then four electrons of each element will make covalent bonds. One electron of the 5A group element is free. In this way, as we increase doping, the number of free electrons will also increase. Hence, this material is called an n-type semiconductor and electrons are the majority charge carriers.

  • When we do the doping of a 3A group element with Silicon (Si) or Germanium (Ge), then three electrons of each element will make covalent bonds. But there will be a shortage of one electron because of the 3A group element. This absence of an electron is known as a hole. In this way, as we increase doping, the number of holes will also increase. Hence, this material is called a p-type semiconductor and holes are the majority of charge carriers.

  • In most electronic devices and in Integrated Circuits, we use semiconductor materials. Among these, the most commonly used semiconductor material is silicon (Si). For optical devices and very high-speed devices, we use semiconductors like Gallium Arsenide (GaAs) and related compounds.

  • In intrinsic semiconductors, the conductivity is poor and there are no impurities. If we add the impurities to the intrinsic semiconductor, then the conductivity will increase. This material is called an extrinsic semiconductor. The other names of extrinsic semiconductors are doped semiconductors and impurity semiconductors.

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