Difference between Intrinsic and Extrinsic Semiconductors

In this article, we will discuss all the important difference between intrinsic and extrinsic semiconductors along with their basic introduction.

Semiconductors play a vital role in the field of electronics and they bridge the gap between conductors and insulators in terms of resistivity and conductivity. With a negative temperature coefficient, the electrical resistance of semiconductors increases with decreasing temperature and vice-versa. Additionally, their conductive or resistivity properties can be changed by introducing suitable metallic impurities, called doping.

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.