Explain how dopants affect the conductivity of a solid, how one can make a material n type or p type and which dopants are likely to render a material ptype or n type. Explain how dopants affect the conductivity of a solid, how one can make a material n type or p type and which dopants are likely to render a material ptype or n type. Solution semiconductors which are made up of pure silicon or germanium without any impurities are called Intrinsic semiconductors. Semiconductors which are doped with some kind of impurity to improve their fuctioning or conductivity or resistivity etc are called extrinsic semiconductors. There are two types of semiconductors which are 1) p-type semiconductors - in these types of semiconductors the doping material which is used is a trivalent substance. In a normal Si/Ge semiconductors, these are tetravalent which means these contains four electrons in their outermost shell and when a trivalent substance replaces a Si/Ge atom in the crystal it creates a HOLES, these show the lack of electron or can be realted to positive charge. Thats why such semiconductrs are known as p-type semiconductrs. The trivalent substance which is doped must belong to the III group, for example Aluminium( Al ), indium( In ) etc. 2) n-type semiconductors - in these types of semiconductors the doping material which is used is a pentavalent substance. In a normal Si/Ge semiconductors, these are tetravalent which means these contains four electrons in their outermost shell and when a trivalent substance replaces a Si/Ge atom in the crystal, so there will be an extra electron, these show the lack of electron or can be realted to positive charge. Thats why such semiconductrs are known as n-type semiconductrs. The pentavalent substance which is doped must belong to the V group, for example phosphorous( P ), arsenic ( As )etc .

1. Explain how dopants affect the conductivity of a solid, how one can make a material n type or p
type and which dopants are likely to render a material ptype or n type.
Explain how dopants affect the conductivity of a solid, how one can make a material n type or p
type and which dopants are likely to render a material ptype or n type.
Solution
semiconductors which are made up of pure silicon or germanium without any impurities are
called Intrinsic semiconductors. Semiconductors which are doped with some kind of impurity to
improve their fuctioning or conductivity or resistivity etc are called extrinsic semiconductors.
There are two types of semiconductors which are
1) p-type semiconductors - in these types of semiconductors the doping material which is used
is a trivalent substance. In a normal Si/Ge semiconductors, these are tetravalent which means
these contains four electrons in their outermost shell and when a trivalent substance replaces a
Si/Ge atom in the crystal it creates a HOLES, these show the lack of electron or can be realted to
positive charge. Thats why such semiconductrs are known as p-type semiconductrs. The trivalent
substance which is doped must belong to the III group, for example Aluminium( Al ), indium( In
) etc.
2) n-type semiconductors - in these types of semiconductors the doping material which is used
is a pentavalent substance. In a normal Si/Ge semiconductors, these are tetravalent which means
these contains four electrons in their outermost shell and when a trivalent substance replaces a
Si/Ge atom in the crystal, so there will be an extra electron, these show the lack of electron or
can be realted to positive charge. Thats why such semiconductrs are known as n-type
semiconductrs. The pentavalent substance which is doped must belong to the V group, for
example phosphorous( P ), arsenic ( As )etc