Definition: Semiconductors are widely used in electronics to make components such as diodes, transistors, thrusters, integrated circuits as well as semiconductor lasers. A ‘semiconductor’ is a material whose properties lie between conductors and insulators. The resistance in semiconductor decreases as there is an increase in temperature because as the temperature is increased, the electrons present in the valence band get excited and jumps into the conduction band, which increases the conductance and hence, resistance decreases.
A semiconductor is usually a solid chemical element or compound that can conduct electricity under some conditions, making it a good medium for the control of electrical current. Its conductance varies depending on the current or voltage applied to a control electrode. Semiconductor is use for manufacturing chips.
A semiconductor device can perform the function of a vacuum tube having hundreds of times its volume. A single integrated circuit (IC), such as a microprocessor chip, can do the work of a set of vacuum tubes that would fill a large building and require its own electric generating plant.
Ex: arsenic, carbon (C), silicon (Si) all are semiconductors.
Electrical properties of Semiconductor
• The resistance of semiconductor decreases as the temperature increases, or you can say that semiconductors have a negative temperature coefficient of resistance.
• The resistivity of a semiconductor lies between the conductor and the insulator.
• The electrical conductivity of a semiconductor is affected when some amount of impurity is added to it.
Types of semiconductor
A semiconductor is of two types- extrinsic and intrinsic
The semiconductor in its pure form is known as an intrinsic semiconductor. In technical terms, we can say that in intrinsic semiconductor the number of holes is equal to a number of electrons.
When an impurity is added into the pure semiconductor, then its charge carrier gets increases and the semiconductor is known as an extrinsic semiconductor.
Depending upon the type of impurity added the extrinsic semiconductor can be classified as follows:
The term n-type refers to the negative charge of the electron. In an n-type semiconductor, electrons are the majority carrier, whereas holes are the minority carrier i.e. electron concentration is more than hole concentration.
The term p-type refers to the positive charge of the hole. In a p-type semiconductor, holes are the majority carrier and electrons are the minority carrier. Also, hole concentration is more than electron concentration.
Difference between n-type semiconductor and p-type semiconductor
|In this type of semiconductor, pentavalent impurities are added like P, Bi etc.
||In this type of semiconductor, trivalent impurities are added like B, Al etc.
|The term n-type refers to the negative charge of the electron.
||The term p-type refers to the positive charge of the hole.
|In this, the impurity atom donates one electron, hence they are also known as donor type semiconductor.
||In this, the impurity atom can accept one electron, hence they are also known as an acceptor type semiconductor.
|In this, electrons are the majority carrier and holes are the minority carrier.
||In this, holes are the majority carrier and electrons are the minority carrier.
|In this, the Fermi energy level is near the conduction band.
||In this, the Fermi energy level is near the valence band.
|They have a larger electron concentration than hole concentration.
||They have a larger hole concentration than electron concentration.
|When there is a rise in temperature, the n-type semiconductors easily donates an electron from donor energy level to the conduction band.
||When there is a rise in temperature, the p-type semiconductors easily accepts an electron from the valence band to donor energy level.
Difference between extrinsic and intrinsic semiconductor
|The semiconductor in its pure form is known as an intrinsic semiconductor.
||The semiconductor formed by adding impurity is known as an extrinsic semiconductor.
|The conductivity of these semiconductors is low.
||The conductivity of these semiconductors is high.
|In these semiconductors, the energy gap is very small.
||In these semiconductors, the energy gap is more than the pure semiconductors.
|These semiconductors are not practically used.
||These semiconductors are practically used.
|In this, the number of free electrons is equal to a number of holes.
||In this, the number of free electrons is not equal to a number of holes
|In this, the Fermi energy level lies in between the valence band and the conduction band.
||In this, the Fermi energy level shifts either towards valence band or towards conduction band.
|Conductivity increases with increase in temperature.
||Conductivity depends on the amount of impurity added.
|It has bad electrical characteristics.
||It has good electrical characteristics.