PN junctions and diodes
Which statement correctly describes the depletion layer of a PN junction in thermal equilibrium?
- AMany majority carriers are gathered there
- BElectrons and holes are both present at high, equal densities
- CThere are almost no carriers, and the charges of ionized impurities remain
Show answer and explanation
Answer: C. There are almost no carriers, and the charges of ionized impurities remain
Near the junction, electrons and holes diffuse and recombine, leaving a region with almost no carriers. This is the depletion layer: negatively charged acceptor ions remain on the p side and positively charged donor ions on the n side, creating the built-in electric field.
- A. The depletion layer is a region from which majority carriers have been swept out.
- B. There are almost no carriers in the depletion layer.
- C. Correct. Carriers are depleted, and the charges of fixed ions remain.