When a p-n junction is formed (BEFORE any external bias is applied), a thin region near the junction develops where the mobile charge carriers are depleted, leaving only fixed ions. This region is called the

1. NCERT §14.5.1 describes p-n junction formation. 2. When p and n materials are joined, free electrons (from the n side) and free holes (from the p side) DIFFUSE across the junction and RECOMBINE near it. 3. This leaves behind FIXED ionised donor atoms on the n side (positive) and FIXED ionised acceptor atoms on the p side (negative) — a charge double layer near the junction. 4. The thin region around the junction that has been swept clean of mobile carriers is the DEPLETION REGION (also called the space-charge region). Typical width: a few hundred nm. 5. The fixed ions set up an internal electric field that opposes further diffusion, establishing equilibrium. 6. Other options name unrelated concepts. _Source: NCERT Class 12 Physics Part 2, Ch 14, §14.5.1 (p-n junction formation, depletion region), p. 10–11._