For P-type semiconductor, the dopant is

In a P-type semiconductor material, holes are generated because trivalent impurity atom has one less electron than surrounding silicon atom. Thus, leaving a vacancy in a covalent bond that acts as a hole. Presence of hole does not make the semiconductor material positively charge because in an impurity atom, no. of electron and proton is equal before and after the doping, and the same applies for the silicon atom.

Thus, p-type semiconductor crystal remains neutral.

Important Points:

• Extrinsic P-type Semiconductor is formed when a trivalent impurity is added to a pure semiconductor
• Example of trivalent impurity are Boron, Gallium and Indium
• Trivalent impurity like boron, have 3 valence electrons
• Each atom of the impurity fits in the silicon crystal by forming covalent bonds with the surrounding silicon atoms
• The dopant boron atom has one less electron than surrounding silicon and thus vacancy is generated that acts as a hole