Semiconductor – Properties, Types and uses

We all might listen this word “semiconductors” right!!! Here we are going to in detailed article related to semiconductor properties, types and uses. To understand the properties of a semiconductor material we should know some fundamental related to the semiconductor material. We also know types of semiconductor and uses of the semiconductor.

So, we are going to learn step by step for better understanding.

What is semiconductor material?

In simple words, a semiconductor is a substance which has the resistivity between conductor and insulator. In general, the conductor has very low resistivity and insulator has nearly infinite resistivity. The semiconductor has the resistivity between 10^(-4) to 0.5 Ωm.

After the invention of the transistor using semiconductor materials, it replaced almost all vacuum tube application. Because of some useful properties of semiconductor materials many electronic devices are made up which are extremely useful in electrical circuits. Diode, Transistor, MOSFET, TRIAC, DIAC, and some other devices are examples where semiconductors are used.

Note that semiconductor is not decided only with the resistivity. Semiconductors have some properties which we are going to learn now.

What are the properties of semiconductors?

All basic properties of semiconductor material are listed below:

⇒ The resistivity of semiconductor material is more than insulator and less than a conductor.

⇒ Semiconductors have a negative temperature coefficient of resistance i.e. the resistance of a semiconductor decreases with the increase in temperature and vice-versa. For example, germanium is actually an insulator at low temperatures but it becomes a good conductor at high temperatures.

⇒ When a suitable metallic impurity (e.g. arsenic, gallium etc.) is added to a semiconductor, its current conducting properties change appreciably.

⇒ Electrical properties of semiconductor: semiconductors are in their neutral state behaves like poor conductors but there are some techniques to flow current through semiconductors. By doping semiconductor, it behaves like a conducting material and allows the current to pass through it.

⇒ In certain semiconductors, excited electrons can relax by emitting light instead of producing heat. These semiconductors are used in making of the light-emitting diode. which is the optical property of a semiconductor.

We can better understand properties of the semiconductor by Energy band.

Energy band for semiconductor

Semiconductors are those materials whose conductivity is lies between conductor and insulator. We can understand this by this energy band theory. In semiconductors, energy band is almost filled and conduction band is almost empty. We require some energy for move electrons from valence band to conduction band.

In a semiconductor, the energy gap is very small as shown in the figure. [In insulator material, the energy gap is so high that electron cannot pass through this gap. In conductors, valence band and conduction band are overlapping each other means there is no gap between that.] In short, the semiconductor has

• Filled valance band
• Empty conduction band
• Small energy gap (nearly  1eV )

At low temperature, the semiconductor valence band is completely filled and conduction band is empty so that it behaves like an insulator or a poor conductor. At a high temperature or even at room temperature, some electrons are passes to the conduction band form valance band. These increase the conductivity of the semiconductor. With the increase in the temperature, the conductivity of semiconductor increases.

Effect of temperature on the semiconductor

The conductivity of semiconductor material changes with the variation of temperature. This may be an important point for the semiconductor material. Here we see in detail about the effect of temperature on a semiconductor. We will see the effect on the semiconductor with two temperature.

1. At absolute zero temperature: At absolute zero temperature, all electrons are tightly held by semiconductor atoms. At this temperature, the co-valance bonds are so strong that there are no free electrons available. Therefore, at this temperature semiconductor crystal behaves like an insulator.

2. At above absolute zero temperature: When the temperature rises, some of the co-valance bonds are break due to thermal energy. Breaking bonds creates free electrons. So some few electrons exist in the semiconductor which can flow current through it. This is also called as, “with the increase in temperature, the resistance of the semiconductor decreases”.

Commonly used semiconductor materials

There are many semiconductors are available but some have practical applications in electronics. Silicon (Se) and Germanium (Ge) are widely used semiconductors. These semiconductors are widely used because the energy required by this two material for release electron from their valance band is too small. Silicon requires 1.1eV and germanium require 0.7eV for release electron from their conduction band. Silicon and germanium are the basic examples of semiconductors.

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Types of semiconductor

Semiconductors are generally divided into two types:

• Intrinsic semiconductor
• Extrinsic semiconductor

Now we go through in detail about the types of semiconductor.

Intrinsic semiconductor

A semiconductor in extremely pure form is called an intrinsic semiconductor.

In an Intrinsic semiconductor, the electron-hole pair created even at room temperature. In this type of semiconductor, When the voltage applied between this material, current passes through the material due to free electrons and holes. You can refer to this figure.

Free electrons are produced due to the breaking of the co-valance bond by thermal energy. At the same time holes are created in the co-valance band. Therefore, total current passes through semiconductor are the sum of current due to electrons and holes.

Current passes through the external wire is only depended upon electron. So you might think what about holes? Right!!!. For that refer above figure, holes being positively charged move towards the negative terminal B. As the holes reach the negative terminal electrons enter the holes, thus canceling them. At the same time, at terminal A, electrons are attracted away from the atom to the battery terminal. Hence, new holes are created at terminal A and repeat this process. So the main property of intrinsic semiconductor is current is passing through this type of semiconductor by holes and electron both.

Extrinsic semiconductor

Intrinsic semiconductors have a poor conductivity at the room temperature. For the increase in their conductivity impurities are added to the semiconductor material. This type of semiconductor having some impurities called extrinsic semiconductor.

The process of adding impurities in the semiconductor is called as doping. The main purpose of doing is to increase the numbers of the electrons or holes in the semiconductor crystal. Depending upon the impurities added, p-type or n-type semiconductor can be decided.

When pentavalent impurity added to the semiconductor material, a large number of free electrons are produced in the semiconductor. This type of semiconductor called n-type semiconductors. You can also refer difference between p type and n type semiconductor material.

When trivalent impurity added to the semiconductor material, holes are created into the semiconductor. This type of semiconductor called n-type semiconductor.

So here the property of extrinsic semiconductor is that current is passing through semiconductor by only electrons.

Uses of semiconductor

Semiconductors are extremely useful in making of electronic devices. Semiconductors are used to make diode, BJT, MOSFET, photocell, UJT, JFET, TRIAC, DIAC and many others. The transistor which is made up from the semiconductor is widely used as an electric switch in circuits. It also uses in an amplifier circuit. Semiconductors is used in solar technology. The temperature sensor which used in air conditioners is made with semiconductor devices. You have to check out this detailed- applications of semiconductor

Conclusion

Hope you know everything about basic properties and types of semiconductor. We saw semiconductor is a material which conductivity is lie between conductor and insulator. Semiconductors have poor conductivity at low temperature. With the increase in the temp, the conductivity of the material increases. Silicon and Germanium (Ge)  are common semiconductors which are used widely in electronics.

We can control the conductivity of the semiconductor material easily which is beneficial for making such devices from that. Diode, transistor, MOSFET, photocell and other devices are made up from semiconductor materials. We saw the types of semiconductor. Intrinsic semiconductors are pure semiconductors and extrinsic semiconductor are semiconductors which contains some impurities.

Hope you enjoyed this article. If you have any doubt regarding the properties of a semiconductor and types of semiconductor then kindly comment below. We also saw uses of semiconductor which help you to understand more about the semiconductor.