In the case of semiconductors the valence and conduction bands have no overlap, energy gap is small

Hole is a vacancy or lack of an electron and can travel through the material. It can only serves as a vacant spot and cannot conduct current

An?intrinsic semiconductor?is an undoped semiconductor. This means that holes in the valence band are vacancies created by electrons that have been thermally excited to the conduction band, as opposed to doped?semiconductors?where holes or electrons are supplied by a ?foreign? atom acting as an impurity.

Doping?is the process of adding impurities to intrinsic semiconductors?to alter their properties. Normally Trivalent and Pentavalent elements are used to dope Silicon and Germanium. When a intrinsic semiconductor?is?doped?with Trivalent impurity it becomes a P-Type?semiconductor.