Question

17. Why are elemental dopants for Silicon or Germanium
usually chosen from group XIII or group XV?​

Answer 1

here wo go

The size of dopant atoms should be such as not to distort the pure semiconductor lattice structure and yet easily contribute a charge carrier on forming co-valent bonds with Si or Ge.Read more on Sarthaks.com - https://www.sarthaks.com/103992/why-are-elemental-dopants-for-silicon-or-germanium-usually-chosen-from-group-xiii-or-group

Answer 2

$Explanation$

So to increase the number of a particular type of charge carriers the Silicon and Germanium crystals that are elements of group XIV, are doped with a small amount of the elements of groups XIII or XV.