Why are elemental dopants for Silicon or Germanium usually chosen from group XIII or group XV? Share with your friends Share 1 Ved Prakash Lakhera answered this Dopants are chosen from either from the 3rd or 5th group of periodic table becuase on adding impurity to the elements of 4th groupsuch as Silicon or Germanium, either there is surplus or defficiency of electrons by one in order to acquire stable atomic structure. Therefore the extrinsic semiconductors made from either Silicon or Germanium are either donor or acceptor types. 3 View Full Answer