Advantages And Disadvantages Of Semiconductors

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SEMI CONDUCTOR:-
Definition:-
Semiconductors are those material in which valence electrons are neither very tightly nor very loosely bound to their atoms, in terms of energy bands. It means that semiconductor has
1) Valence band with few holes.
2) Conduction band with few free electrons.
3) A very narrow energy gap b/w valence and conduction band.
In its pure state semiconductor contains few free electrons in the conduction band.
Characteristics:-
Semiconductors are not electrical conductors or insulators, but act like them, depending on conditions, such as temperature. The properties of semiconductors depend largely on what elements comprises them.

• The value of band gap between valence bond and conduction band in semi-conductor is 1e.v.
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• At room temperature, valence bond gains thermal energy and e transit from valence band to conduction band (very few) then conductivity happens. At room temperature, the semi-conductor material are poor conductors.

Use of Semiconductor:-

• Semiconductor material is used in the manufacturing of electrical components.
• Semiconductor material is used in the manufacturing of electronic devices such as transistors and diodes.
• Silicon and Germanium are basic elements to make electronic device.

Types of Semiconductor:-

They can be ordered into mainly two types
1) Intrinsic semiconductors
2) Extrinsic semiconductors.
Intrinsic semiconductors:-

• A semiconductor in its pure state is called intrinsic semiconductor.
• It has very poor conductivity.
• It is a single element not mixed with anything else.

Extrinsic semiconductor:-
• A doped semiconductor is called extrinsic semiconductor
• It cause changes in the conductivity of this material.
• A silicon crystal is an extrinsic semiconductor if every element of the crystal is not a silicon
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Its n region contains free electrons as majority carriers and p-region contains holes as majority carriers.

DIFFUSION:- After the formation of junction, because of their random motion electrons in the n-region move to the p-region and recombine with the hole. This process is called diffusion.

DEPLETION REGION:- As a result of diffusion, a charge less region is formed around the junction in which charge carriers are not present. This region is called depletion region.

POTENTIAL BARRIER OR JUNCTION BARRIER:-

As free electrons move across the junction from n-region to p-region, a positive charge is built on the n-side of the junction and the negative charge on the p-side. Due to these ions a potential difference develop across the depletion region, called potential barrier. Its value is 0.7 volts in case of Silicon 0.3 volts in case of Germanium.

• P-type and N-type material are joined by the process of diffusion.
• When e- and hole combines it forms barrier layer or depletion layer and release energy.
• If Si is base material then barrier voltage would be 0.7 V and if Ge then 0.4 V.
• Silicon is temperature stable but Germanium is

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