Definition of semiconductor: Substances that have less electrical conductivity than conductors and more than insulators are called semiconductors. Definition of semiconductor in physics, Substances through which electricity cannot flow at a temperature of zero degrees Celsius, but as the temperature rises, the flow of electricity through the material increases, are called semiconductors.
Definition of semiconductor
Definition of semiconductor in physics, Substances through which electricity cannot flow at a temperature of zero degrees Celsius, but as the temperature rises, the flow of electricity through the material increases, are called semiconductors. As much as there are substances in nature, all substances have certain properties. Some substances transmit electricity, while others do not. Again some transmit less electricity. Depending on the electrical conductivity of all these substances, the substance is divided into three parts.
Semiconductor: Substances through which electricity cannot flow normally at normal temperature, but partial increase in electric current as the temperature rises, are called semiconductors. At normal temperatures, all these substances become like insulators. That is, no electricity can flow through the semiconductor at a normal temperature. Now the question that may come to the mind of many is, if electricity cannot flow through semiconductors, then how do different types of electronic devices work.
If you want to know the answer to this question, you have to read this article in its entirety so that you can know the definition of semiconductor and how it works. Details of semiconductors will be discussed in this article. And various types of information about electronics will be published on this website. So you will be connected with this website all the time to know different types of information about electronics.
Conductors: All the substances that conduct electricity are called conductors. Electricity can always flow through all these substances. The resistance to these substances is much less. So electricity can flow through these substances in any environment. E.g., Copper, Silver, Gold. The cables we use to carry electricity in our homes are pure conductors. The resistance of these cables is much less.
So electricity can flow very easily without any kind of interruption. However, we must always remember one thing – the thicker the cable, the more electricity will flow through the cable. And if the cable is thin, the resistance of that cable will be higher. As a result, the flow of electricity through the cable will be less.
Insulators: Substances through which electricity cannot flow are called insulators. The resistance of all these substances is very high, so no electricity can flow through the insulator. All of these materials are usually mounted on top of electrical cables. As a result, the electric cable does not give an electric shock to any human or animal. For example, porcelain, ebonite, dry wood, paper and glass, mica are these insulators.
So far we have generally known about definition of semiconductor, conductors, and insulators. Today we will discuss semiconductors in detail. So let’s get started.
Atomic structure of semiconductor
To know about definition of semiconductor in detail, we first need to know about the atomic structure of semiconductor material. If we know in detail about the structure of semiconductor atoms, we can easily know about the properties of semiconductor materials. The semiconductor definition in physics has been discussed above. Now we will discuss the atomic structure of semiconductor material according to electron theory.
We hope you find the definition of semiconductor in physics very easy to read semiconductor. And you can learn about how electricity is transmitted through semiconductors and in what ways. To understand the definition of semiconductor in physics, first, you need to know about the electron configuration of an atom. If you don’t know the electron configuration of an atom, then definitions of semiconductors do not know well. So let us discuss in detail about the electron configuration of an atom for all to understand.
We all know that an object is made up of a combination of some basic substances. Sometimes an object is made up of a mixture of more basic substances. Again an object is made with only one basic substance. Objects that are composed of a combination of more basic elements are called compounds. And objects that are made up of a single substance are called elemental substances. A total of 118 elements have been identified in the world so far. Of these, 94 are found in nature, the remaining 24 are artificially created.
Generally, the number of protons in an atom of an element is fixed. That is, the atomic number of each of them is the same and the atomic number of different elements is different. Therefore, any element can be identified by the number of protons in general. Some of the 118 elements have semiconductor elements. Silicon and germanium are one of the semiconductor elements. Today we will discuss the electron configuration of the atoms of silicon and germanium.
We all know that the electrons in an atom are in a specific orbit. If there are four electrons in the last orbit of an atom, then that atom or substance is called a semiconductor.
The structure of silicon and germanium
At the center of each atom is the nucleus, and within the nucleus are positively charged protons and non-charged neutron particles. The negatively charged electrons of the atom revolve in circular and elliptical orbits around the nucleus. When electrons revolve in a circular and elliptical way, they continue to rotate in orbit following a certain formula.
The formula is 2n ^ 2. This formula adheres to every electron atom. Here n denotes the number of orbits. n = 1,2,3,4 ….. When, n = 1, meaning the first energy level. n = 2, here, the second energy level is denoted. n = 3, here, the third energy level is meant. That is, from this we understand that the electrons in orbit change as the value of n changes. So let’s see how the number of electrons in the cell changes.
The formula mentioned earlier is- 2n^2. n = 1 is- 2*(1)^2 = 2. That means the first orbit can have 2 electrons. If n = 2 then -2 * (2) ^ 2 = 8, that is, a total of eight electrons can be located in the second energy level. If n = 3 – 2 * (3) ^ 2 = 18, that is, a maximum of 18 electrons can be located in the third energy level.
Silicon electron configuration:
We all probably know that the atomic number of silicon is 14. That means the number of electrons in silicon is 14. These 14 electrons are arranged in different energy levels according to the 2n ^ 2 formula. According to the formula, there will be 2 electrons in the first energy level and a total of 8 electrons in the second energy level. A total of 10 electrons will be in the first and second energy levels.
The remaining 4 electrons will be in the third energy level. Although a total of 18 electrons can be located in the third energy level, silicon does not have enough electrons and its last four electrons will be located in the third energy level. We know that if there are a total of 4 electrons in the last orbit, then that substance is a semiconductor. Since silicon has 4 electrons in its last orbit, silicon is a semiconductor material.
Germanium electron configuration:
The atomic number of germanium is 32. Therefore, the number of electrons in germanium is 32. According to the formula, there will be 2 electrons in the first energy level, 8 in the second energy level, and 18 in the third energy level. A total of 28 electrons will be in orbit 1,2,3. The remaining 4 electrons will be in the last orbit. That is, the fourth will be at the power level. We can also see from the electron configuration of germanium that there are 4 electrons in its last orbit. So we can say that germanium is a semiconductor substance.
Now we will discuss the flow of electricity through a semiconductor material.
The effect of temperature on the conductivity of semiconductor
The flow of electricity through the semiconductor depends on the temperature. It has been said before that pure semiconductors do not transmit electricity. So let’s discuss this in-depth.
The specific resistivity of the semiconductor is between the conductor and the insulator. The conductivity of a semiconductor changes as the temperature changes. The most widely used silicon energy gap is 1.1eV. And the energy gap of germanium is 0.7eV. At zero degrees the valence band of silicon and germanium is filled with electrons, but the conduction band is empty. Conduction bands do not hold any electrons. In this condition, semiconductor materials provide very high-quality resistance.
That is to say, they do not have conductivity. In this case, the semiconductors act as insulators. When the semiconductor is moved above a temperature of zero degrees Celsius, some of the electrons in the valence band gain more energy than the energy gap, and the conduction band leaves. This creates a large number of free electrons and holes in the covalent bond of the semiconductor. This reduces the resistivity of the semiconductor.
Therefore, very little current flows through the semiconductor. As the temperature increases, the electrons move from the valence band of the semiconductor to the conduction band. As a result, the flow of electricity through the semiconductor increases. Since the conductivity of a semiconductor increases with increasing temperature, its resistive temperature coefficient is negative.
Semiconductor energy band theory and diagram
Semiconductors are substances that cannot conduct electricity but increase electrical conductivity as the temperature rises, and very little electricity can flow. No electricity can flow through a semiconductor at a temperature of zero degrees Celsius. But at normal room temperature, it contains a small number of free electrons, which can cause very little electricity to flow through the semiconductor.
According to the definition of energy band, the valence band is almost full and the conduction band is almost empty. And the amount of energy gap between the valence band and the conduction band is very small. As the temperature between semiconductor materials increases, the amount of energy gap between the valence band and the conduction band decreases.
Applying a small amount of electric field can transfer electrons from the valence band to the conduction band. In short-
- The valence band remains full
- The conduction band is almost empty
- The amount of energy gap between the balance band and the conduction band is very small. Calculated it will be 1 eV.
At low temperatures the valence band is full and the conduction band is empty. As a result, the semiconductor acts as an insulator at low temperatures. That is, no electricity can flow through the semiconductor. At room temperature, some electrons go beyond the valence band to the conduction band. This results in the semiconductor displaying a small amount of electrical conductivity. As the temperature increases, a large number of electrons move from the valence band to the conduction band.
This increases the conductivity between the semiconductors. Therefore, the resistance of a semiconductor can be said to have a positive temperature co-efficient resistance. When electricity flows in any part of a semiconductor material, a small part of it spreads to other places. This type of substance has 4 electrons in its outer orbit. And the resistance of the semiconductor ranges from 10 ^-4 to .5 ohms per meter. Carbon, silicon and germanium are used more in semiconductor materials.
Types of semiconductors
There are mainly two types of semiconductors.
- Intrinsic Semiconductor
- Extrinsic semiconductor
Extrinsic semiconductors can again be divided into two parts.
- N-type semiconductor
- P-type semiconductor
Intrinsic semiconductor definition
Intrinsic semiconductor is called silicon and germanium. Because they do not contain any waste or any other element. The semiconductor behaves like a non-conductive at a temperature of zero degrees Celsius. If the temperature in the semiconductor is increased, the electrons in their valence band exceed the conduction band, for which the value of the resistance of the semiconductor decreases.
As a result, the intrinsic semiconductor behaves like a partial conductor. The energy gap between the valence band and the conduction band of silicon is 1.1 electron volts. And the energy gap between the valence band and the conduction band of germanium is .7 electron volts. The energy gap between the valence band and the conduction band of the intrinsic semiconductor is much smaller.
For this, the electron conduction band of the valence band of the intrinsic semiconductor at room temperature can go. The transfer of electrons from the valence band to the conduction band results in the formation of a positive charge in the valence band, and creates a hole. For this, we can say that the hole always displays a positive charge.
We all know that Intrinsic Semiconductor does not conduct electricity at a temperature of zero degrees Celsius. And as the temperature increases the electrons in the valence band begin to transfer to the conduction band. A small amount of electricity can flow through the intrinsic semiconductor at room temperature.
Let’s see how electricity flows through the intrinsic semiconductor at room temperature:
When a semiconductor is carried above a temperature of zero degrees Celsius, the electrons in the valence band absorb the temperature. Absorption of temperature causes excitation in electrons. At one stage of the excitation, the electrons in the valence band begin to transfer to the conduction band. At room temperature, some amount of electrons move into the conduction band.
When a high-temperature electric field is applied to the semiconductor, it is observed that the electrons of the conduction band go to the anode and the holes of the valence band go to the cathode. Thus it is seen that electricity flows through the semiconductor through the participation of both the hole and the electron of the semiconductor. Due to these reasons, electricity flows through the semiconductor.
Extrinsic Semiconductor definition
Extrinsic Semiconductor is made by mixing an appropriate amount of any product and any other substance as an adulterant. The most commonly used intrinsic semiconductor is –
- Elements with five valence electrons
- An element with three valence electrons
The five constituent elements are arsenic, antimony, phosphorus.
The three constituent elements are gallium, aluminum, boron, and indium.
Atoms that have five electrons in their last orbit are called donor atoms. This is because the conduction band of pure germanium donates an electron. Atoms that have three electrons in their last orbit are called receptive atoms. Because it takes an electron from the germanium atom. Semiconductors are divided into two parts based on adulterated materials. One is a p-type semiconductor, and the other is an n-type semiconductor.
The generation of hole and electron in an intrinsic semiconductor
Behaves like a semiconductor insulator at a temperature of zero degrees Celsius. Because it does not have a free charge carrier. Moreover in pure semiconductor crystal formation as well as atoms are tightly bound by strong covalent bonds through electron sharing.
At temperatures above zero (at room temperature) the covalent bonds of pure semiconductors break down and some electrons move away from the semiconductor crystal. As a result, a hole is created in the place from where the electron moved. The hole carries a positive charge. That is, from the valence band to the electron conduction band, a hole is created in the valence band.
Holes are formed when an electron moves elsewhere. Then an electron jumped from there and went to the space. Then an electron jumped from that place and went to the empty place. Thus a hole will be created in the last other position due to the movement of electrons.
Here, holes are formed due to the movement of electrons in the valence band. Pure semiconductors have an equal number of free electrons and holes. The free electrons can move around in the crystal. When a free electron arrives at the location of a hole, charge neutrality occurs at the junction of the electron and the hole. This is called the Recombination of Holes and Electrons. For thermal excitation, new electron-hole pairs are formed and recombination continues.
What do you mean by doping in a semiconductor
A pure silicon crystal is called an intrinsic semiconductor. Intrinsic semiconductors do not have enough free electrons and holes. As a result, it is not possible to work by creating current flow as per the demand in different applications. For this reason, waste or adulterated atoms are added to them to increase the conductivity of pure semiconductors. This creates a large number of free electrons or holes in the crystal atom.
Doping is the process of attaching adulterated atoms to intrinsic semiconductors. The crystalline material formed in this way is called an extrinsic semiconductor. Usually, an adulterated atom is mixed between 10^8 atoms. In the case of semiconductors, gallium, indium, aluminum, and baron are usually mixed as three-composite adulterated atoms. In the case of semiconductors, arsenic, antimony, phosphorus, and bismuth are usually mixed as five-composite adulterated atoms.
P-type semiconductor definition
When a triangular atom is attached to a pure silicon or germanium atom as a waste, its three valence electrons form a covalent bond by sharing the valence electrons of three nearby silicon. But its valence cannot form a bond with the fourth silicon due to the lack of electrons. The result is the creation of a hole. Thus, the combination of each triangular atom creates a hole. The new semiconductor formed to carry this hole positive charge is called P-type semiconductor.
More doping results in more holes originating. Therefore the majority charge carrier of P-type semiconductor is the hole and the minority charge is an electron. The triangular atom is called the receptor atom. This is because each hole receives one electron during recombination. Such acceptor atoms are aluminum, boron and gallium. The structure of P-type semiconductor is shown in Fig.
Boron has been used as an adulterant substance here. Covalent bonds are formed by sharing three electrons of boron with four electrons of germanium. But a hole was created because one of Boron’s hands was empty.
N-type semiconductor definition
When a five-composite atom of pure silicon crystal is inserted as an adulterant. Then the four electrons of the five covalent atoms form a covalent bond by sharing the valence electrons of the nearest four silicon atoms. And completes its valence band by eight electrons. As a result, an extra electron is released from the atom with five valances. This free electron then moves to the conduction band.
In this way, the electrons of the conduction band can be increased by increasing the amount of doping. As a result, electrons become the majority charge carriers. On the other hand, the amount of holes produced under thermal energy becomes negligible. Since electrons carry a negative charge, a semiconductor formed in this way is called an N-type semiconductor. An atom with five components is called a donor atom. This is because they generate electrons in the conduction band. These donor atoms are arsenic, antimony, and phosphorus.
Here pure semiconductor silicon is mixed with antimony as a five-composite substance. The four electrons of silicon are bonding with the four electrons of antimony. But Antimony is free because it does not have the opportunity to share an electron.
Charge carrier in a semiconductor
Germanium or silicon has no free charge carrier at a temperature of zero degrees Celsius. However, when the amount of temperature is increased above the room temperature, some covalent bonds are broken due to heat. The result is the formation of electrons and hole pairs. These are called charge carriers caused by thermal energy. The amount of such produced carriers is very low. When a pure germanium is converted to a P-type semiconductor by an adulterated atom.
Then the hole produced by the adulterated atom in the P-type semiconductor and the hole created by the heat energy increase the total number of holes. And a small number of electrons created by heat energy are present along the hole. Therefore, in P-type semiconductors the majority charge carrier hole and the minority charge carrier are electrons. As shown in the figure-
Similarly, when pure germanium is converted to an N-type semiconductor by a donor adulterated atom, the N-type semiconductor generates a large number of electrons. These electrons combine with the electrons created by heat energy to increase the total number of electrons. On the other hand, with that large number of electrons, some amount of hole charge due to heat energy exists. So the majority charge carrier of N-type semiconductor is an electron and the minority charge carrier is the hole. Which is shown in the figure.
Conclusion of definition of semiconductor
This article discusses in depth the definition of semiconductor. In addition, this article discusses the atomic structure of semiconductors, Types of semiconductors, and charge carriers.
- Feynman, Richard (1963). Feynman Lectures on Physics. Basic Books.
- “184.108.40.206 The “hot-probe” experiment”. ecee.colorado.edu. Retrieved 27 November 2020.
- Shockley, William (1950). Electrons and holes in semiconductors : with applications to transistor electronics. R. E. Krieger Pub. Co. ISBN 978-0-88275-382-9.