The depletion region of a pn junction is a layer that
- A. contains a very high concentration of free carriers
- B. has been swept clear of mobile charge carriers, leaving fixed ions and a potential barrier
- C. conducts better than the rest of the crystal
- D. consists only of electrons
Explanation
Electrons diffusing across the junction recombine with holes, leaving exposed fixed ions on both sides and a region with almost no mobile carriers, so it acts as an insulator. The resulting internal field forms a potential barrier of about 0.7 V for silicon and 0.3 V for germanium. Forward biasing narrows this region and reverse biasing widens it.