TRANSPORT PHENOMENA IN SEMICONDUCTOR

Presented byChakrapani Tripathi

Branch-E.C-2

Material

We know that material is classified in three part

Conductor Insulator Semiconductor

Energy Band Diagram

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Semiconductor

Semiconductor materials are those material which conductivity is greater than insulator and less than conductor.

Semiconductor is divided in two parts Intrinsic semiconductor Extrinsic semiconductor

Intrinsic Semiconductor A semiconductor in an extremely pure form is

known as intrinsic semiconductor The Si , Ge are the two most widely used

intrinsic semiconductor The intrinsic semiconductor at absolute zero

behave as an insulator At room temp some covalent bond break ,when

a covalent bonds break the electron becomes free to move through the crystal.

Intrinsic semiconductorIntrinsic Semiconductor

Conduction In Intrinsic Semiconductor

When we apply voltage across a piece of intrinsic semiconductor material, the thermally generated free electron in the conduction band are attracted towards the positive end .

The current constituted due to movement of free electron is called as electron current.

Extrinsic Semiconductors

Adding some amount of impurity atoms in pure or intrinsic semiconductor , we an change its conductivity.this process is called doping.

These impurity material can be of two types

Donor impurity Acceptor impurity

Accepter Impurity(Trivalent Impurity)

When the dopant is trivalent atom it is called as accepter impurity.

The atom containing three valence electron that is trivalent atom.

Some example of trivalent atom is Boron,Gallium,Aluminium and Indium

Adding trivalent atomWhen we add trivalent atom in semiconductor

material so P-type semiconductor formed some trivalent atom are given below

e.g – Boron ,Gallium ,Aluminium and Indium

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Donor impurity(pentavalent impurity)

When the dopant is a pentavalent atom it is called the donor impurity.

The atom containing five valence electron that is pentavalent atom.

Some example of pentavalent atom is Arsenic,Phosphorous and Antimony.

N-type

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When we add pentavalent atom in semiconductorSo N type semiconductor is formed.

Some pentavalent atom are given belowe. g-arsenic,phosphorous,antimony e.t.c.

Conduction in P-type semiconductorConduction in N-type semiconductor

Electrical Properties of semiconductor

Negative temp. co-efficient of resistance Doping Resistivity

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