A slab of p-type or n-type semiconductor, howsoever flat, will have roughness much larger than the interatomic crystal spacing. Hence, on joining p – and n-type slabs continuous contact at the atomic level is not possible and the two will not join together. In fact the junction will behave as a discontinuity.
Class 12 Physics Chapter 14 Semiconductor Electronics Session 2024-2025.
Why can’t we take one slab of p-type semiconductor and physically join it to another slab of n-type semiconductor to get p – n junction?
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Physically joining p-type and n-type slabs doesn’t form a proper p-n junction because their crystal lattices remain discontinuous at the interface, causing defects. True p-n junctions are created by doping a single crystal to ensure lattice continuity, enabling the essential diffusion of charge carriers and formation of a depletion region.
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