Answer:
Aluminium has three electrons, so a hole will be created when silicon is doped with it.
p-type semiconductors
When a tetravalent atom such as Si or Ge is doped with a trivalent impurity such as Al, B, In, etc., the dopant atom has one less electron than the surrounding atoms of Si or Ge. Thus, the fourth atom of the tetravalent atom is free and a hole or a vacancy is generated in the trivalent atom. In such materials, the holes are the charge carriers and such semiconductors are termed as p-type semiconductors.
