Which of the following elements is typically used in the doping of the semiconductor silicon?

The story behind the answer

Boron is correct because it has three valence electrons, one fewer than silicon’s four. When boron atoms replace silicon in the crystal lattice, each creates a “hole” (a missing electron) that can move through the lattice, carrying positive charge. This makes the silicon p-type: its dominant charge carriers are holes. Boron’s acceptor energy level sits just above the valence band, so at room temperature it easily creates holes and boosts conductivity in a controlled way.

Context: Doping tailors a semiconductor’s electrical behavior. Trivalent elements like boron make p-type silicon, while pentavalent elements like phosphorus or arsenic make n-type (extra electrons). Oxygen and carbon are often unwanted impurities, and iron introduces trap states, not useful carriers. Memory tip: “B for Boron, B for ‘hole-Borrowing’—p-type.”