Semi-Conductors

Semiconductors
Metals which have conductivity less than conductors and more than insulators or resistivity more than conductors and less than insulators are known as semiconductors.
e. g silicon, germanium etc
Types of semiconductors
1)Intrinsic semiconductors
2) Extrinsic semiconductors
Intrinsic semiconductors
When in pure germanium or silicon the amount of impurity level is less than 1 part in10^8, that semiconductor is known as intrinsic semiconductor
Extrinsic Semiconductor
When in pure silicon or germanium, impurity of element is added in very small proportion, it is called extrinsic semiconductor
The process of adding impurity element in pure semiconductor is known as doping
Extrinsic semiconductors may be of two types :-
1)N-type Semiconductor
2)P-type Semiconductor
N-Type Semiconductors
 When in pure germanium or silicon the impurity of the penta valent element like arsenic, antimony or phosphorus is added in very small definite proportion, N-type semiconductor results



Energy band diagram for N-type semiconductor

P-type Semiconductor
 When in pure germanium or silicon, impurity of the trivalent element having three valence electrons is added in small definite proportion, P-type results.
Energy band diagram of P-type semiconductor



Applications
 1)Diodes
 2)I.C
 3)Transistor