P-n Junction Formation

NCERT explains that when p-type and n-type materials are joined, the large concentration difference drives electrons to diffuse from the n-side into the p-side and holes from the p-side into the n-side. Near the junction these diffusing carriers recombine, leaving behind immobile ionized donor and acceptor atoms and stripping the region of mobile carriers. This carrier-free zone is called the depletion region, and the exposed fixed ions set up an internal electric field and a potential barrier that eventually halts further diffusion. The option about a conduction channel is wrong because the region actually lacks free carriers rather than concentrating them. The option about an inversion layer is wrong because that concept belongs to field-effect devices and requires an external gate voltage, not spontaneous junction formation. The option calling it an undoped neutral zone is wrong because both sides are doped; the region is depleted of mobile carriers but full of fixed charged ions. As stated in NCERT Class 12, Chapter 14, diffusion and recombination create the depletion layer and barrier potential. A consistency check confirms equilibrium is reached when the barrier field exactly opposes further diffusion.