Definition of Intrinsic Semiconductor
An intrinsic
semiconductor is a pure form of a semiconductor material that is free from
any impurities or doping elements. The number of charge carriers, i.e. holes
and electrons in intrinsic semiconductors is only determined by the inherent
properties of the semiconductor itself, without any influence from impurities.
It is important to note that the number of free electrons is equal to the
number of holes within an intrinsic semiconductor. Some popular examples of
intrinsic semiconductors are germanium
(Ge) and silicon (Si).
Definition of Extrinsic Semiconductor
An extrinsic semiconductor
is formed when a small amount of chemical impurity is added to an intrinsic
semiconductor. This process is known as doping
and it enhances the conductivity of semiconductors. Therefore, an extrinsic semiconductor
is also known as a doped semiconductor.
Extrinsic semiconductors are further classified into the following
two types based on the type of doping performed. They are:
- N-Type Semiconductors – This type of extrinsic semiconductor is formed when a pentavalent impurity is introduced to an intrinsic semiconductor.
- P-type Semiconductors – This type of extrinsic semiconductor is formed by adding a trivalent impurity to a pure semiconductor.
Differences between Intrinsic and Extrinsic Semiconductors
The following comprehensive table lists the crucial differences
between intrinsic and extrinsic semiconductors:
Key |
Intrinsic
Semiconductor |
Extrinsic
Semiconductor |
Basic |
It is the purest form of semiconductor material without any impurities. |
It is a semiconductor doped with added chemical impurities. |
Classification |
There is no classification of intrinsic semiconductors. |
Extrinsic semiconductors are of two types namely, P-type and N-type
semiconductors. |
Doping |
Intrinsic semiconductor involves no doping or impurity addition. |
Extrinsic semiconductors involve doping or adding a small amount of
impurity. |
The density of charge carriers |
An intrinsic semiconductor has an equal number of electrons and holes. |
Extrinsic semiconductors have different numbers of electrons and holes
in P-type and N-type. |
Electrical conductivity |
Intrinsic semiconductors have low electrical conductivity. |
Extrinsic semiconductors have high electrical conductivity. |
Conductivity dependence |
The conductivity of intrinsic semiconductors is dependent on
temperature only. |
The conductivity of extrinsic semiconductors is dependent on
temperature and impurity level. |
Conductivity at 0 K |
Intrinsic semiconductors do not conduct at 0 K temperature. |
Extrinsic semiconductors can conduct at 0 Kelvin as well. |
Production of charge carriers |
Intrinsic semiconductors have charge carriers produced only due to
thermal excitation. |
The charge carriers in extrinsic semiconductors are produced due to
thermal excitation and chemical impurities. |
Operating temperature |
Intrinsic semiconductors have a low operating temperature. |
Extrinsic semiconductors have a high operating temperature. |
Fermi level at 0 K |
At 0 Kelvin, the fermi level of intrinsic semiconductors lies between
conduction and valence bands |
At 0 Kelvin, the fermi level of extrinsic semiconductors changes based
on the type of semiconductor. |
Charge carriers ratio |
Intrinsic semiconductors have the ratio of majority and minority
carriers equal to 1. |
The ratio of majority and minority carriers differs for different extrinsic
semiconductors. |
Practical examples |
Crystalline silicon and germanium are examples of intrinsic
semiconductors. |
Silicon and germanium mixed with impurities like As, P, Bi, Sb, In,
B, Al, etc. are extrinsic semiconductors. |
Considering all this, the differences between intrinsic and extrinsic semiconductors, considering charge density, doping, conductivity, and more, provide information on their unique properties and applications in the field of electronics. The knowledge of these differences is very important for utilizing their potential in various technological advancements.
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