For n-type semiconductors, we have,
ne >> nh
(14 3)
(ii)  p-type semiconductor
This is obtained when Si or Ge is doped with a trivalent impurity
like Al, B, In, etc The dopant has one valence electron less than
Si or Ge and, therefore, this atom can form covalent bonds with
neighbouring three Si atoms but does not have any electron to
offer to the fourth Si atom So the bond between the fourth
neighbour and the trivalent atom has a vacancy or hole as
shown in Fig