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Home > News & Articles > Extrinsic Semiconductor: Definitions, Examples, Facts, Types, Uses, and Sample Questions
Updated on 03rd July, 2023 , 6 min read
Extrinsic semiconductors are created when intrinsic semiconductors are combined with a trace quantity of a chemical impurity. Doped semiconductors or impurity semiconductors are other names for them. In general, semiconductors are crystalline or amorphous substances with electrical conductivity between a conductor and an insulator. Doping changes the semiconductor's electrical characteristics, making it suitable for use in electronic devices like diodes and transistors.
Semiconductors are substances that fall between insulators like glass and conductors like copper in terms of electrical conductivity. Silicon and Germanium, commonly referred to as elemental semiconductors, are typical examples of semiconductors. Examples of compound semiconductors include phthalocyanines with dopants, anthracene, GaAs, CdSe, and CdS. Semiconductors are mostly used in electronic devices such as transistors, integrated circuits, and diodes. These gadgets have a wide range of uses since they are reasonably priced, small, dependable, and power-efficient. Extrinsic semiconductors and intrinsic semiconductors are the two primary categories of semiconductors.
Extrinsic semiconductors are those semiconductors that are created when an intrinsic semiconductor is combined with a controlled and limited amount of chemical impurity. Impurity semiconductors, or doped semiconductors, are other names for them. The conductivity of semiconductors is increased through doping. Doping is the purposeful addition of an undesirable impurity, and dopants are the impurity atoms. N-Type semiconductors and P-Type semiconductors are the two other forms of extrinsic semiconductors.
Pure silicon and germanium doped with impurities like As, P, Bi, Sb, In, B, Al, etc. are examples of extrinsic semiconductors.
The following are the two types of extrinsic semiconductors-
By doping an inherent semiconductor with an electron donor element during production, N-type semiconductors are produced. The word "n-type" refers to the electron's negative charge. Electrons make up the bulk of carriers in n-type semiconductors, whereas holes make up the minority. For n-type silicon, phosphorus or arsenic are frequent dopants. The Fermi level of an n-type semiconductor is higher than that of an intrinsic semiconductor and is located nearer the conduction band than the valence band.
Examples: Phosphorus, arsenic, antimony, etc.
An intrinsic semiconductor is doped during production with an electron acceptor element to produce P-type semiconductors. The positive charge of a hole is referred to as its p-type. P-type semiconductors have a higher hole concentration than electron concentration in comparison to n-type semiconductors. Electrons make up the minority of carriers in p-type semiconductors, whereas holes constitute the majority. Boron or gallium are frequently used as p-type dopants for silicon. The Fermi level for p-type semiconductors is below the intrinsic level and is situated nearer the valence band than the conduction band.
Examples: Boron, Aluminum, Gallium, etc.
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The main distinctions between intrinsic and extrinsic semiconductors are shown in the table below-
|
Intrinsic Semiconductor |
Extrinsic Semiconductor |
|
For intrinsic semiconductors, the pure form of semiconductors is employed. |
Extrinsic semiconductors are created by doping pure semiconductors. |
|
At room temperature, electrical conductivity is low. |
High conductivity of electricity. |
|
The quantities of electrons and holes are the same. |
The quantities of electrons and holes are not equal. |
|
Solely dependent on temperature. |
Dependent on the impurity level and temperature. |
|
There is no more categorization. |
Classified as both p and n-type. |
|
Example: Pure Ge |
Example: Ge is doped with Al, P, or As. |
The majority of electronic gadgets are made mostly of extrinsic semiconductors. The following are some of the uses of extrinsic semiconductors-
Solution: Pentavalent dopants are atoms that have five valence electrons. They are employed in the production of N-Type semiconductors by doping semiconductors.Examples include arsenic (As), phosphorous (P), and antimony (Sb). The term "trivalent dopants" refers to atoms containing three valence electrons. Consider the elements aluminium (Al) and boron (B).
Solution: Doping is the technique of introducing certain impurities to an intrinsic semiconductor in order to increase the carrier concentration. Dopants are atoms that are employed as an impurity.
Solution: An N-Type Extrinsic Semiconductor is created when a pentavalent impurity is added to an intrinsic semiconductor.
Solution: Extrinsic semiconductors are ones that have certain impurities doped into them. The impurity modifies the semiconductor's electrical characteristics, improving its suitability for electronic components like diodes and transistors. The dopant that is added to the material is selected in a way that prevents distortion of the initial lattice of the pure semiconductor. When a tiny amount of an appropriate impurity is introduced to a pure substance, the conductivity of the mixture is multiplied by many. Since the dopants only occupy a small portion of the original semiconductor's crystal, it is essential that their size be approximately identical to that of the semiconductor atoms.
Solution: The answer is that semiconductors are crystalline solids with electrical conductivities that lie between those of insulators and conductors. In semiconductors, the energy gap between the valence and conduction bands is rather tiny. Compared to conductors, semiconductors make it a bit harder for electrons to get up to the conduction band.
Solution: The tiny energy band gaps of elements like silicon and germanium make them good conductors. Additionally, because they are both tetravalent elements, they each have four valence electrons.
Solution: When certain impurities are added to a pure semiconductor, extrinsic semiconductors are produced. Semiconductors come in two varieties: P-type and N-type.
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By - Nikita Parmar 2023-08-25 09:48:44 , 11 min readAns. Germanium and silicon are the two components that make up an excellent semiconductor. There are four valence electrons in each element.
Ans. Pure silicon and germanium doped with impurities like As, P, Bi, Sb, In, B, Al, etc. are examples of extrinsic semiconductors.
Ans. An n-type semiconductor is created when a pentavalent impurity is introduced to a pure semiconductor. This is due to the four valence electrons that a pure semiconductor contains. One electron becomes free and accessible for conduction when a pentavalent impurity is introduced. This is what causes n-type semiconductors to develop.
Ans. The assertion is untrue. The conductivity of the semiconductor is temperature and impurity dependent. The conductivity rises as the temperature rises or as contaminants are introduced.
Ans. The process by which free electrons and holes are produced in pairs is known as the production of carriers. Recombination of carriers is the removal of free electrons and holes, according to the definition. When a free electron from the conduction band enters a hole in the valence band, both the free electron and hole are eliminated.
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