Here, you will get to see semiconductor and its types.
Semiconductor are a type of substance in which there is a resistivity (10-4 to 0.5 ohm) between the conductor and insulator. Such as germanium, silicon, selenium, carbon.
However semiconductors are more broadly defined on the basis of energy bands. As you know semiconductor is such a substance which the valence band is almost full and the conduction band is almost empty.
So because of this there is a very small energy gap (≃ 1eV ) and separates the two. The forbidden energy gap is very small in semiconductors, 0.7 eV for germanium and 1.1 eV for silicon.
Therefore their valence electrons require relatively small energy to cross the conduction band. Even at room temperature some valence electrons can gain enough energy to enter the conduction band and thus become free electrons.
However , at this temperature number of free electrons is very small. Therefore, at room temperature, semiconductors are neither a good conductor nor a good insulator.
What is the most commonly used semiconductor material?
There are many semiconductors available, but very few of them are use in electronics. The two most commonly use semiconductor materials are GERMANIUM (Ge) and SILICON (Si).
It is use more because the energy required to break their covalent bond is very less. 0.7 eV for germanium and 1.1 eV for silicon.
For GERMANIUM (Ge) :
The atomic number of germanium is 32. Therefore the number of electrons in the 1st orbit of germanium atom is 2 the number of electrons in the 2nd orbit is 8 the number of electrons in the 3rd orbit is 18 and the number of electrons in the 4th orbit is 4.
Note that germanium atom has 4 valence electrons.
For SILICON (Si) :
The atomic number of silicon is 14. Therefore the number of electrons in the 1st orbit of silicon is 2 the number of electrons in the 2nd orbit is 8 and the number of electrons in the 3rd orbit is 4.
Again , a silicon atom has 4 valence electrons. There are two types Semiconductor 1. Intrinsic semiconductor 2. Extrinsic semiconductor
For Types of electron emission click here.
For What is rectifier in electronics click here.
Intrinsic and extrinsic semiconductor
Extrinsic semiconductor
Extrinsic semiconductor has impurity added. It is the type of semiconductor in which some impurity is added to make the conduction of current possible.
The process of adding the impurities in a semiconductor is know as doping. The impurity may be different atoms like indium, phosphorus, boron, bismuth etc.
There are two types of extrinsic semiconductor and they are
- n- type semiconductor
- p – type semiconductor
Define n type semiconductor
When pentavalent impurity is add to an intrinsic semiconductor then we get n-type semiconductor. Pentavalent impurity 5 valence electrons out of which 4 electrons are use to make co-valent bond with neighboring silicon atom.
The other electron now gets additional energy to become free electron. As there are more number of electrons create as compare to holes. This type of semiconductor is know as n-type semiconductor.
The majority charge carries in n-type semiconductors are electrons and holes are the minority charge carries. Example of pentavalent impurities are phosphorus, arsenic, antimony.
Define p type semiconductor
When trivalent impurity is add to a pure semiconductor then we get p-type semiconductor. The example of trivalent impurities are boron, gallium, indium.
The majority charge carrier in p-type semiconductor are holes and minority charge carrier is electrons. As there are more number of holes as compare to electrons. So, this type of semiconductors are know as p-type semiconductor.
Intrinsic semiconductor
Intrinsic semiconductor are the semiconductor materials in pure form. This type of semiconductor have either only silicon or germanium atoms.
In case of intrinsic semiconductor whenever temperature of even or additional energy is given. Then the co-valent bond between the silicon atoms breaks down.
This breaking of co-valent bond creates and electron hole pair. So, a hole is an empty space or vacancy created by the valence electron.
When this electron becomes free electron by getting energy in semiconductor the current flow takes place due to both electron as well as holes.
Some useful properties are found in semiconductors which are widely use in electronic circuits. For example – Transistor, is a semiconductor device that rapidly replaces the vacuum tube filled in all applications. Transistor is one of the family of semiconductor device.
Semiconductor are use in many types of electronic devices and it is use to make some devices like transistor, diode, triode, integrated circuit (IC) and power transmission etc. So it was about semiconductors, Hope you will understand whatever information I have given to you about semiconductor.