semiconductor, conductor, insulator, doping, n and p type seminconductor with diagrams :D

2. ELECTRICAL CONDUCTIVITY
Presented by- Bhupender Singh
13ECE06

3. CONTENT
 Electrical conductivity
Energy Band structures
Conductor
Insulator
 Semiconductors
 Doping
Intrinsic semiconductor
Extrinsic semiconductor
n-type materials
p-type materials

4. ELECTRICAL CONDUCTIVITY
 Conductivity defines a material’s ability to conduct
electricity.
 Electric current can flow easily through a material
with high conductivity.
 In order of conductivity: Conductor, semiconductor,
insulator are comes.

5. ENERGY BAND STRUCTURES

6. CONDUCTOR
valence band only partially
filled.
next allowed empty band
overlaps with it.
All the atoms jumps to
conduction band.
Examples copper, iron.

7. INSULATOR
Energy gap is very wide.
Energy gap in Insulator is
more than 9 eV
electricity can’t conduct
Examples wood, plastic

8. SEMICONDUCTOR
 It Lies between insulators and
conductors are called
Semiconductor .
 Examples Si, Ge
 Energy gap is very small.
 They are of two types :
1. INTRINSIC
2. EXTRINSIC

9. DOPING
 A semiconductor , which is in its extremely pure form , is known
as Intrinsic semiconductor.
 Germanium and Silicon are most widely used semiconductor.
 Silicon crystal contribute 4 valence electron.
 The atoms are bounded by covalent bond.

10. INTRINSIC SEMICONDUCTOR
 These are undoped
semiconductor.
 It has equal number of
electrons and holes.
 These are also called pure
semiconductors.
 Ex.=Si, Ga.

11. EXTRINSIC SEMICONDUCTOR
 These are doped semiconductors.
 It has not equal number of electrons and holes.
 This semiconductor obtained by doping of trivalent and
pentavalent impurities in a tetravalent semiconductor.
 These are also known as impure semiconductors.

12. Extrinsic Semiconductor
Two types of impurity atoms are added to the
semiconductor
Atoms containing 5
valance electrons
(Pentavalent impurity
atoms)
e.g. P,As,Sb,Bi
Atoms containing 3
valance electrons
(Trivalent impurity atoms)
e.g. Al,Ga,B,In
N-type semiconductor P-type semiconductor

13. N-TYPE MATERIAL
Donor (n-type) impurities:
 dopant with 5 valence electrons (e.g. P, As, Sb)
 four electrons used for covalent bonds with surrounding Si
atoms, one electron “left over”
 left over electron needed only small amount of energy to lift it
into conduction band (0.05ev in Si)
 “N-type semiconductor”, has conduction electrons, no holes.

14. P-TYPE MATERIAL
Acceptor (p-type) impurities:
 dopant with 3 valence electrons (e.g. B, Al, Ga, In)
 only 3 of the 4 covalent bonds filled
 vacancy in the fourth covalent bond hole.
 “p-type semiconductor”, has mobile holes, very few mobile
electrons.