SEMICONDUCTORS

INTRODUCTION

The classification of the materials by means of the physics, they are:

1. SOLID
2. LIQUID
3. GAS
but the classification of the materials by means of electrical terminology there are:
1. CONDUCTORS
2. INSULATORS
3. SEMICONDUCTOR
now we discuss about the materials which are classified by electrical quantities.
conductor: the conductor is a material that allows or conducts the electricity through it. the conductor has more than four electrons in the outermost orbit of the atom.
insulators: insulator is a material that opposes the flow of electricity through it. the insulator has less than four electrons in the outermost orbit of the atom.
semiconductor: semiconductor is a material that has both properties of the conductor and insulator. the semiconductor has four electrons in the outermost orbit of the atom.

SEMICONDUCTOR

already we know that the semiconductor has both properties of the conductor and insulator.furtherly the semiconductors are classified into two types they are:
1. intrinsic
2. extrinsic
intrinsic: the intrinsic means it is the purest form of the semiconductors and it doesn't have any other impurities in it.
extrinsic: the extrinsic semiconductor is formed by adding impurities to the intrinsic semiconductor(i.e adding impurities to the pure form of the semiconductor).adding of the impurities is called as dopping. these are further divided into two types they are:
1. N-type semiconductor
2. P-type semiconductor
N-TYPE SEMICONDUCTOR
The N-TYPE SEMICONDUCTOR is formed by adding an impurity to an intrinsic semiconductor, the impurity atom should have the five electrons in the outermost orbit to form an n-type semiconductor. the silicon is the pure form of the semiconductor, it has the four electrons in the outermost orbit. if we add the arsenic atom to the silicon crystal then it is formed as an n-type semiconductor. the arsenic atom has the five electrons in the outermost orbit so if we add this to the silicon crystal then the four electrons of arsenic are joined in the silicon crystal but the remaining one electron in the outermost orbit of arsenic remains as a free electron. then the conduction will happen by this remaining free electron. in this n-type of semiconductor, the majority of carriers are electrons because there is an excess electron in this semiconductor. the majority of carriers mean the current carriers are electrons in this semiconductor. the formation of n-type semiconductor is as shown below_ _ _P-TYPE SEMICONDUCTOR
The P-TYPE SEMICONDUCTOR is formed by adding an impurity to an intrinsic semiconductor, the impurity atom should have the three electrons in the outermost orbit to form a p-type semiconductor. the germanium is the pure form of the semiconductor, it has the four electrons in the outermost orbit. if we add the boron atom to the silicon crystal then it is formed a p-type semiconductor. the boron atom has the three electrons in the outermost orbit so if we add this to the germanium crystal then the three electrons of the boron atom are joined in the silicon crystal but the one hole is formed because four electrons are needed to complete the formation of germanium crystal but one electron is missing to complete this crystal form so the one hole is created in the crystal. in this p-type of semiconductor, the majority of carriers are holes because there is a shortage of one electron so instead of one electron the hole is formed in this semiconductor. the conduction will happen by the holes in this p-type semiconductor. the formation of the p-type semiconductor is as shown below_ _ _