what are 3 methods of doping? what type of doping is used in p-type semi comductor ,explain in detail...............
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doping: Conductivity of semiconductors is too low to be of practical use. their conductivity is increased by adding of suitable impurity. this process is called doping...doping can be done with an impurity which is electron rich or electron deficient. Extrinsic semi conductors are of 2 types..
a)n type semiconductor: it is obtained by adding trace amount of 5A group elements (p,As,Sb) to pure si or Ge by doping.
when p,As,Sb or Bi is added to si orGe some of the si or Ge in crystal are replaced by p or As atoms. Out of five valency electrons of p or As ,four electrons will be used for bonding with si or Ge atoms while the fifth electron serves to conduct electricity.
b)p type semiconductors :it is obtained by doping i.e 3a group elements (B AL Ga)when Ga is added to Ge some of the Ge atoms in the crystals are replaced by Ga atom will be used for bonding with Ge while the fourth valence electron is missing and is called electron hole or electron vacancy .this vacancy on an atom in the structure migrates from one atom to another.hence it facilitates the electrical conductivity.
a)n type semiconductor: it is obtained by adding trace amount of 5A group elements (p,As,Sb) to pure si or Ge by doping.
when p,As,Sb or Bi is added to si orGe some of the si or Ge in crystal are replaced by p or As atoms. Out of five valency electrons of p or As ,four electrons will be used for bonding with si or Ge atoms while the fifth electron serves to conduct electricity.
b)p type semiconductors :it is obtained by doping i.e 3a group elements (B AL Ga)when Ga is added to Ge some of the Ge atoms in the crystals are replaced by Ga atom will be used for bonding with Ge while the fourth valence electron is missing and is called electron hole or electron vacancy .this vacancy on an atom in the structure migrates from one atom to another.hence it facilitates the electrical conductivity.
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An extrinsic semiconductor is an improved intrinsic semiconductor such as germanium or silicon with a small amount of impurities added by a process called as Doping.
Doping with suitable impurities alters the electrical properties of the semiconductors and improves its conductivity.
The impurities added are called as Doping agents or dopants.
Doping process produces two types of semiconductors:
They are
i)n-type semiconductor
2) P-type semiconductor.
P-type semiconductor:
The purpose of p-type doping is to create an abundance of holes.
Example: Germanium: it is doped with a trivalent atom such as those from group III of periodic table. The result is that an electron is missing from one of the four covalent bonds formed by impurity atom.Thus there is a hole associated with the atom and it can accept an electron to complete the fourth bond. when a sufficiently large number of such impurity atoms are added ,the number of holes increases as compared to the excited electrons.
Thus, in P-type semiconductors, the holes are majority carriers, while electrons are the minority charge carriers.
The most type of p-type dopants for germanium or silicon are the group III elements like Boron,Aluminium, Gallium, and Indium. Since these three electron atoms accept an electron to complete the crystalline structure they are called as acceptor atoms.
Doping with suitable impurities alters the electrical properties of the semiconductors and improves its conductivity.
The impurities added are called as Doping agents or dopants.
Doping process produces two types of semiconductors:
They are
i)n-type semiconductor
2) P-type semiconductor.
P-type semiconductor:
The purpose of p-type doping is to create an abundance of holes.
Example: Germanium: it is doped with a trivalent atom such as those from group III of periodic table. The result is that an electron is missing from one of the four covalent bonds formed by impurity atom.Thus there is a hole associated with the atom and it can accept an electron to complete the fourth bond. when a sufficiently large number of such impurity atoms are added ,the number of holes increases as compared to the excited electrons.
Thus, in P-type semiconductors, the holes are majority carriers, while electrons are the minority charge carriers.
The most type of p-type dopants for germanium or silicon are the group III elements like Boron,Aluminium, Gallium, and Indium. Since these three electron atoms accept an electron to complete the crystalline structure they are called as acceptor atoms.
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