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Submitted ByoMD. Mominuz Zaman

ID#141-15-3103oSharmin Sultana Jeesa

ID#141-15-3219

Semiconductor

Semiconductor

oA Semiconductor is a substance which has resistivity 10-4 to 0.5 Ω-m and the resistivity of Semiconductor lies between conductors and insulators.

oThe example of Semiconductor are silicon(si), germanium(Ge) etc.

Properties of Semiconductors

o The resistivity of Semiconductor lies between insulator and conductor.

o Semiconductor has negative temperature coefficient.

o If metallic impurity is added to the Semiconductor its current carrying properties changes significantly.

Bonds in Semiconductors

oThe bonds in semiconductor are formed by covalent bond.

oElectron configuration of Silicon is Si(14)-1s22s22p63s23p2.

Types of Semiconductor

Semiconductor are basically 2 types:oIntrinsic SemiconductoroExtrinsic Semiconductor

Intrinsic SemiconductoroA semiconductor is an extremely pure form is known as intrinsic semiconductor.

Extrinsic Semiconductor

oWhen impurity is added with pure semiconductor to increase the current carrying properties then it is called extrinsic semiconductor .

oThis added impurity is very small in amount. Basically, 1 atom is added for 10⁸atoms of pure semiconductor to make extrinsic semiconductor.

Types of Extrinsic Semiconductor

Depending upon the type of impurity added, extrinsic semiconductor are classified as-on-type Semiconductorop-type Semiconductor

n-type SemiconductoroWhen a small amount of penta-valent material is added to the semiconductor then it is known as n-type semiconductor.

oElectron Configuration of Arsenic is , As(33)-1s22s22p63s2

3p63d10

4s24p3

p-type SemiconductoroWhen a small amount of trivalent material is added to the semiconductor then it is called p-type semiconductor.oThe Electron Configuration of  Gallium is Ga(31)-1s22s22p63s23p63d104s24p1

Majority & Minority Carriers

oFor n-type material the free electrons are considered as majority carriers & the holes are minority carriers.

Majority & Minority Carriers

• For p-type material the holes are considered as majority carriers & the free electrons are minority carriers.

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