- In today’s article, we are going to study about ‘ semiconductor ‘ How beneficial it is and what is intrinsic and extrinsic semiconductor. And hence We will also read about some more topics like types of semiconductor, extrinsic semiconductor, intrinsic semiconductor, propagation of holes, energy band in Semiconductor etc given in Detail. So, take your notebooks in you hand and get ready to study physics in an easy and sorted way.
They are those materials in which valance band is completely filled and empty conduction band is separated from the Valence band by a small empty gap. So that even at room temperature few of electron are able to jump over this gap. And hence they can reach in conduction band so that the materials show some conductivity even at room temperature. ΔEg <3 mev.
Types of semiconductor
- Intrinsic semiconductor
- Extrinsic semiconductor
1. Intrinsic semiconductor
A pure semiconductor called intrinsic semiconductor like Ge and Si(silicon) lattice. The germanium and silicon have four Valence electron. As we know energy atom try to keep eight electron in its outermost orbit for stability. When Ge form a lattice or crystal then Ge atom make four covalent bond by sharing four electron by its nearest neighbour atom as shown in fig
At the temperature t=0k the Ge behaves like a insulator because no free electrons are available. Ge has 0.72 ev energy band gap between conduction band and Valence band. At room temperature some of electron take thermal energy and goes in conduction band. So a vacancy create in Valence band. This vacancy is behaves like a positive charge and it is called hole.
In intrinsic semiconductor the number of free electron He is equal to Number of holes so He= nh = ni …(1)
Where ni is called intrinsic carrier concentration. When we apply a potential on Ge substance as shish in fig-
The total current flow in semiconductor equal to sum of current due to flow of electron and hole. The charge of a hole is 1.6×10^19 C and electron is 16×10^-19 C.
Propagation of hole in semiconductor
In a semiconductor Vb and C.B are separated by a forbidden energy gap. The Valence band is completely filled and conduction band is empty. Then at room temperature electron is in the Valence band gain thermal energy and jump over the forbidden energy gap to reach the conduction band. The electrons reaching the conduction band leave behind equal number of holes in the valence band. These holes create empty energy levels in the Valence band. The hole can be filled by an electron from nearby energy levels in the Valence band. When electron fills the hole, another hole is created at the site from where the electron goes to fill the hole.
When a small amount of impurities of a suitable material added in a pure semiconductor like gallium and silicon then and impure semiconductor will create and this is known as extrinsic semiconductor. The impurity adding process is known as doping. In the doping we add one atom of impurity in 10 million of pure semiconductor atom.
In general, the impurity atoms are taken from pentavalent atoms like phosphorus arsenic and Sb, and trivalent atom like Boron aluminium, indium, gallium.
So our article is finished and after completely reading this article, one can easily tell what is Semiconductor. And we have also discussed some more topics types of semiconductor, extrinsic semiconductor, intrinsic semiconductor, propagation of holes etc.
So one can say that they got a detailed information about semiconductor and basic information about other topics.
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