p-type doping: Doping with trivalent elements boron, aluminum, or gallium creates a hole in the silicon lattice because these elements have one less valence electron than silicon. The hole can be thought of as a positively charged carrier, and increasing the concentration of holes creates a p-type semiconductor.

Doping increases the number of electrons or holes, which lowers the resistance and improves the conductivity of the material. In pure silicon, the number of carriers is limited, poor conductivity; after doping, the increase in free carriers makes it easier for electrons or holes to move, and conductivity is enhanced.

Formation of p-n junctions: When p-type and n-type semiconductors come into contact, p-n junctions are formed at their junction. p-n junction properties (e.g., a built-in electric field) further control the flow of electric current, and are the basis for many electronic devices (e.g., diodes, transistors).

Temperature effects: Temperature variations also affect the conductivity of doped semiconductors, but doping pre-sets the conductive properties of the material primarily by changing the intrinsic carrier concentration.

By precisely controlling the type and concentration of doping, engineers are able to design silicon wafers with specific electrical properties, a critical step in the fabrication of a wide variety of electronic and optoelectronic devices.