How do boron and phosphorus change silicon’s electrical conductivity?

Pure silicon is an intrinsic semiconductor with high electrical resistance at room temperature. To improve its conductivity, specific impurities are introduced through a process called doping. Boron and phosphorus change silicon's electrical properties in the following ways:

• Boron: As a trivalent atom with three outer electrons, boron acts as an acceptor. When substituted for a silicon atom in the crystal lattice, it creates a positively charged site known as a "hole." This results in a p-type (positive) semiconductor, where conduction occurs through the migration of these holes.123
• Phosphorus: As a pentavalent atom with five outer electrons, phosphorus acts as a donor. When it replaces a silicon atom, four of its electrons form covalent bonds, while the fifth becomes a free electron available for conduction. This creates an n-type (negative) semiconductor.123

By creating these charge carriers—either free electrons or holes—doping significantly increases the material's ability to conduct electric current, making it essential for modern electronic devices.143