If silicon is doped with a TRIVALENT impurity such as boron (or indium), the resulting semiconductor is

1. Boron is a group-13 element with THREE valence electrons. 2. When a boron atom replaces a silicon atom in the lattice, it can only form three covalent bonds with neighbouring Si atoms. The fourth bond position is left with a 'hole' — a missing electron. 3. Electrons from adjacent Si–Si bonds can hop into this hole, effectively allowing the hole to MOVE through the lattice — current is carried by these holes. 4. Holes become MAJORITY carriers (and they carry positive charge, hence 'p-type'); electrons remain only as MINORITY carriers. 5. The material remains electrically neutral overall because each boron acceptor that captures an electron becomes a fixed negative ion in the lattice. 6. Option B is the n-type recipe (pentavalent dopants). Options C and D contradict the basic doping mechanism. _Source: NCERT Class 12 Physics Part 2, Ch 14, §14.4 (Extrinsic Semiconductor — (ii) p-type), p. 8._