Derivation of expression for the conductivity of a Semi-Conductor

 

Last time we have discussed the conductivity of semiconductor. Let us today derive the expression the expression for conductivity of semiconductor.

In a Semi-Conductor of length (ℓ) and area of Cross-Section. Let ne and nh be the no. of electrons and holes with drift velocities Ve and Vh respectively.

So, the total current in the semi-conductor will be the sum of current due to electrons as well as holes,

i.e.        I = Ie + Ih                                                             (i) Continue reading “Derivation of expression for the conductivity of a Semi-Conductor”

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meaning of the term hole in a semi-conductor

Hole in a semiconductor:

In a semi-conductor the energy gap is of the order of 1eV. At OK, the semi-conductor behaves like an insulator but at room temp the electrons acquire sufficient energy to jump to the conductor band thereby creating a vacancy in the valence band.

            This deficiency or vacancy of electron in the valence band is termed as a hole. It is equivalent to 1 unit of +Ve charge. To fill this vacancy, the nearly electrons present in the valence band jumps to that position. So another hole is created and thus it appears as if the holes are moving. So, in R semi-conductor, electrons move in the conduction band whereas holes in the valence band.

Why doping is done in semiconductors?

The addition of impurity atoms to a pure-semi-conductor is known as doping. The doping is done to increase the conductivity of a pure semi-conductor. It must be noted that the impurity atom is about 1 in every 1010 atoms.

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Difference between n type semiconductor and p type semiconductor

We have already discussed about the concept of semiconductors, their types: intrinsic and extrinsic semiconductors, difference between intrinsic and extrinsic semiconductors and further types of extrinsic semiconductors that are n type semiconductors and p type semiconductors. Today we will discuss the difference between n type and p type semiconductors on point to point basis: Continue reading “Difference between n type semiconductor and p type semiconductor”

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Difference between intrinsic and extrinsic semiconductors

We have already discussed about the concept of semiconductors, their types: intrinsic and extrinsic semiconductors and further types of extrinsic semiconductors that are n type semiconductors and p type semiconductors. Today we will discuss the difference between intrinsic and extrinsic semiconductors on point to point basis: Continue reading “Difference between intrinsic and extrinsic semiconductors”

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Types of extrinsic semiconductors

In last article I have started discussion on extrinsic semiconductor. In today’s article I will discuss the extrinsic semiconductor and its 2 types in detail. As already discussed a doped semi-conductor is known as an extrinsic semi-conductor. It is of 2 types:

a) n-type semiconductor and b) p-type semiconductor

Let us discuss these two types of extrinsic semiconductors in detail: Continue reading “Types of extrinsic semiconductors”

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Semiconductor and its types

Semiconductors:

Semiconductors are the materials whose conductivity lies between insulator and conductors. Their conductivity lies in between insulator and conductors because of the energy band gap. The energy band gap of semiconductor lies in between insulator and conductors. For example for the case of silicon, the semiconductor, the conductivity is 1.1 electron volt.

Types of semiconductors: Continue reading “Semiconductor and its types”

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why insulators do not conduct electricity

In the last article, I have discussed about the conductors, semiconductors and insulators. Today I will discuss why insulators do not conduct electricity or why insulator is insulator?

As I have already discussed that there is energy band gap between valence band and conduction band. This energy band gap is very large in case of insulators. It may be minimum of 3 electron volt or more. Continue reading “why insulators do not conduct electricity”

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Energy Band in a case of Solids

Energy band or energy band gap in solids is defined as the energy gap between the top of the valence band and bottom of the conduction band. The unit of the energy band gap is normally electron-volt (ev). It is denoted by the symbol Eg.

According to Bohr’s atomic model, the electrons revolving around the nucleus are governed by a definite path and hence have a definite energy level so the electrons in an atom have well-defined energy levels. Continue reading “Energy Band in a case of Solids”

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Solids and its types

Solid 

Solid is one of the four forms of matter. Solid does not flow like liquids but all the solids possess the property of elasticity which means that when a deforming force is applied on a solid, it returns to its original position. Since the solids are made up of atoms or molecules, so depending upon their arrangement, they are classified into two categories.

(a)    Crystalline

(b)   Amorphous Continue reading “Solids and its types”

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