What is n type and p …

 n-type semiconductor

• When pure Si or Ge which has four valency electrons is doped with controlled amount of pentavalent atoms, like Arsenic, Phosphorus, Antimony or Bismuth, we get a n-type semiconductor
• The four valence electron from the impure atom will combine with four electrons of the Si or Ge atom to form 4 covalent bonds
• The fifth electron of the impure atom is free to move. Thus, each atom of the impure substance, donates a free electron for conduction. Hence, it is called as donor atom
• Giving the free electron for conduction, the impure atom becomes positively charged, giving rise to a hole
•  Thus in n-type semiconductors, electrons are the majority carriers and holes are minority carriers.

p-type semiconductor

• When pure Si or Ge which has four valency electrons is doped with controlled amount of trivalent atoms, like Gallium, Indium, Boron or Aluminium, we get a p-type semiconductor
• The three valence electron from the impure atom will combine with three electrons of the Si or Ge atom to form 3 covalent bonds
• There will be one unbounded electron in the Ge atom which would try to form a covalent bond with the neighbouring Ge atom
• This Ge-Ge covalent bond creates a deficiency of electron in Ge atom. Thus, creating a hole
• This hole is compensated by the breakage of Ge-Ge covalent bond in the neighbourhood. Hence, electron moves towards the hole, resulting in hole formation at some other place
• The trivalent atoms are called acceptor atoms and conduction of electricity is due to the motion of holes
• Thus in p-type semiconductors, holes are the majority carriers and electrons are minority carriers.