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Difference between P-Type and N-Type Semiconductor
The type of materials whose conductivity is greater than insulators but less than conductors are known as semiconductor materials. In other words, a material is said to be semiconductor, if it has 4 electrons in its outermost shell. The semiconductor materials are broadly classified into two categories viz. intrinsic semiconductors and extrinsic semiconductors.
Extrinsic semiconductors are further classified into two types as −
P-Types Semiconductor
N-Type Semiconductor
In this article, we will compare the P-type and N-type semiconductors by considering various factors such as type of impurity added, nature of doping, majority charge carriers, density of charge carriers, fermi level, etc. But, before going into the actual differentiation of P-type and N-type semiconductor, we will define both types of semiconductor.
What is a P-Type Semiconductor?
A P-type semiconductor is a type of extrinsic semiconductor, which is obtained by adding a trivalent impurity in an intrinsic (or pure) semiconductor. The examples of trivalent impurities are aluminum, gallium, indium, etc. When the trivalent impurity is added to an intrinsic semiconductor, it provides extra holes and these impurities are also known as acceptor impurities. Therefore, the majority charge carriers in the P-type semiconductor are holes.
What is an N-Type Semiconductor?
An N-type semiconductor is also a type of extrinsic semiconductor, which is obtained by adding a pentavalent impurity in an intrinsic semiconductor. The common examples of pentavalent impurities are antimony, arsenic, bismuth, etc. When the pentavalent impurity is added to a pure semiconductor, it provides extra electrons and thus these are also known as donor impurities. In case of N-Type semiconductor, the majority charge carriers are electrons.
Difference between P-Type and N-Type Semiconductors
The following table highlights the major differences between a P-type semiconductor and an N-type semiconductor −
| Basis of Difference | P-Type Semiconductor | N-Type Semiconductor |
|---|---|---|
| Definition | When a trivalent impurity is added to an intrinsic semiconductor, the obtained semiconductor is known as P-type semiconductor. | When a pentavalent impurity is added to an intrinsic semiconductor, the obtained semiconductor is known as N-type semiconductor. |
| Type of impurity added | To obtain the P-type semiconductor, a trivalent impurity such as aluminum, gallium, indium, etc. is added to the pure semiconductor. | The pentavalent impurities such as P, Sb, As, Bi, etc. are added to pure semiconductor to obtain N-type semiconductor. |
| Group of doping element (or impurity) | The elements of group 13 are added as doping element to form a P-type semiconductor. | The elements of group 15 are added as doping element to form an N-type semiconductor. |
| Effect of impurity or doping element | In case of P-type semiconductor, the impurity added creates a vacancy of electron in the structure, known as hole. | In case of N-type semiconductor, the impurity added provides extra electrons in the structure. |
| Alternate name of impurity added | In P-type semiconductor, the doping element is a trivalent element, which can accept electrons from the intrinsic semiconductor. Therefore, the doping element or impurity is also known as acceptor impurity. | In N-type semiconductor, the pentavalent atoms are used as impurity which provide extra electrons. Hence, the doping element is also known as donor impurity. |
| Majority charge carriers | Holes are the majority charge carriers in a P-type semiconductor. | Electrons are the majority charge carriers in an N-type semiconductor. |
| Minority charge carriers | Electrons are the minority charge carries in a P-type semiconductor. | Holes are the minority charge carriers in an N-type semiconductor. |
| Charge density | In case of P-type semiconductor, the number of holes are much more than number of electrons, i.e. Nh >> Ne. | In an N-type semiconductor, the number of electrons are much more than the number of holes, i.e. Ne >> Nh. |
| Movement of majority charge carriers | In a P-type semiconductor, the majority charge carriers are holes (which are positive), thus moves from higher potential to lower potential. | The majority charge carries in an N-type semiconductor are electrons (which are negative), thus moves from lower potential to higher potential. |
| Energy levels | P-type semiconductor has acceptor energy levels very close to the valance band and away from the conduction band. | N-type semiconductor has donor energy levels very close to the conduction band and away from the valance band. |
| Effect of temperature rise | When the temperature of P-type semiconductor is increased, it can easily accept an electron from valance band to acceptor energy level. | When the temperature of N-type semiconductor is increased, it can easily donate an electron from donor energy level to the conduction band. |
| Conductivity | In P-type semiconductors, the conductivity is due to the presence of holes. | The conductivity in the N-type semiconductor is due to the presence of electrons. |
| Fermi level | In a P-type semiconductor, the fermi level lies between the acceptor energy level and the valance band. | In an N-type semiconductor, the fermi level lies between the donor energy level and the conduction band. |
Conclusion
Both P-type and N-type semiconductors are extrinsic semiconductors. However, the key difference between the two is that a P-type semiconductor is obtained by adding the trivalent impurity like aluminum in a pure semiconductor, while an N-type semiconductor is obtained by adding pentavalent impurity like phosphorous in a pure semiconductor.
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