Si or Ge belongs to the fourth group in the
Periodic table and, therefore, we choose the
dopant element from nearby fifth or third
group, expecting and taking care that the
size of the dopant atom is nearly the same as
that of Si or Ge Interestingly, the pentavalent
and trivalent dopants in Si or Ge give two
entirely different types of semiconductors as
discussed below (i)  n-type semiconductor
Suppose we dope Si or Ge with a pentavalent
element as shown in Fig 14