2. Introduction to Semiconductors
DEFINITION -
Semiconductors are materials which have a conductivity between conductors (generally metals) and non-
conductors or insulators (such as ceramics).
IMPORTANCE -
A semiconductor substance lies between the conductor and insulator. It controls and manages the flow of
electric current in electronic equipment and devices. As a result, it is a popular component of electronic chips
made for computing components and a variety of electronic devices, including solid-state storage.
3. What is an N-Type Semiconductor ?
The N-type semiconductor is described as a type of extrinsic semiconductor
doped with a pentavalent (having five valence electrons) impurity element. The
pentavalent impurity or dopant elements are added in the N-type
semiconductor so as to increase the number of electrons for conduction.
Because of the pentavalent impurity in an N-type semiconductor, a number of
loosely bonded electrons populate the lattice structure. As a certain amount of
voltage is applied, these electrons gain energy to break free and cross the
forbidden gap, leaving the valence band to enter into the conduction band. This
results in a very small number of holes being formed in the valence band. The
Fermi level (highest energy level an electron occupies at absolute zero
temperature) is near the conduction band as more electrons enter the
conduction band.
4. What is a P-Type Semiconductor ?
The P-type Semiconductor is formed when a trivalent (having three valence
electrons) impurity such as Gallium and Indium is added to a pure
semiconductor in a small amount, and as a result, a large number of holes are
created in it. These p-type producing impurities are known as Acceptors
because each atom of them creates one hole which can accept one bonded
electron. A positive charge hole is created when the three valence electrons of
the impurity bond with three of the four valence electrons of the semiconductor
and having one electron short, the covalent bond cannot be completed, hence
the missing electron is known as a hole.
5. Differences between P-type and N-type
Semiconductors
In determining the difference between p-type and n-type semiconductors, factors such as doping element, effect of
doping element, the majority and minority carriers in both types are taken into consideration. Additionally, the density of
electrons and holes, energy level and Fermi level, the direction of movement of majority carriers, etc. are also accounted
for in clarifying the disparity between p-type and n-type semiconductors. In this vein therefore, the differences are
outlined thus :
● As a main difference, in n-type semiconductors, the electrons have a negative charge, hence the name n-type.
While in p-type, the effect of a positive charge is generated in the absence of an electron, hence the name p-type.
● In a p-type semiconductor, the III group element of the periodic table is added as a doping element, while in n-type
the doping element is the V group element.
6. Differences between P-type and N-type
Semiconductors
● The electron density is much greater than the hole density in the n-type semiconductor represented as ne >> nh
whereas, in the p-type semiconductor, the hole density is much greater than the electron density: nh >> ne.
● In an n-type semiconductor, the donor energy level is close to the conduction band and away from the valence band.
While in the p-type semiconductor, the acceptor energy level is close to the valence band and away from the conduction
band
● The impurity added in p-type semiconductor provides extra holes known as Acceptor atoms, whereas in n-type
semiconductor impurity provides extra electrons called Donor atoms.
● The Fermi level of the n-type semiconductor rests between the donor energy level and the conduction band while that of
the p-type semiconductor is between the acceptor energy level and the valence band.
7. Comparison Chart
For a more simplified representation of the features of the p-type semiconductor and the n-type
semiconductor, the following chart is provided.
Factor of
Comparison
P-Type Semiconductor N-Type Semiconductor
Group of Doping
Element
Group III element is added as
doping element.
Group V element is added as
doping element.
Effect of Doping
Element
Impurity added creates vacancy
of electrons (holes) known as
Acceptor Atoms.
Impurity added provides extra
electrons and is called Donor
Atom.
8. MORE DIFFERENCES -
Density of
Electrons and
Holes
The hole density is much
higher than the electron
density:nh >> ne.
The electron density is much
higher than the hole density: ne
>> nh.
Type of impurity
added
Trivalent impurity like Al, Ga, In
etc. are added.
Pentavalent impurity like P, As,
Sb, Bi etc. are added.
Movement of
Majority carriers
Majority carriers move from
higher to lower potential.
Majority carriers move from
lower to higher potential
Energy level The acceptor energy level is
close to the valence band and
away from the conduction band.
The donor energy level is close
to the conduction band and
away from the valence band.
9. References
● Tech Target. What is a Semiconductor and what is it used for? 2022 [Cited 2022 Jul 11].
Available from:
https://www.google.com/amp/s/www.techtarget.com/whatis/definition/semiconductor%3famp=1
● Electronic Notes. What is a Semiconductor? 2022. [Cited 2022 Jul 11] Available from:
https://www.electronics-notes.com/articles/basic_concepts/conductors-semiconductors-
insulators/what-is-a-semiconductor.php
● Electronics Desk. Difference Between Intrinsic and Extrinsic Semiconductor. 2022. [Cited 2022
Jul 12] Available from: https://electronicsdesk.com/difference-between-intrinsic-and-extrinsic-
semiconductor.html
● Embibe. Extrinsic Semiconductor: Types, Energy Bands & Applications. 2022. [Cited 2022 Jul
12] Available from: https://www.embibe.com/exams/extrinsic-semiconductor/
● Linquip Technews. Differences Between P-Type and N-Type Semiconductor. 2021. [Cited
2022 Jul 12] Available from: https://www.linquip.com/blog/differences-between-p-type-and-n-
type-semiconductor/?amp=1
