Final answer:
The width of the depletion zone of an unbiased p-n junction depends on dopant densities and the electric field in the zone is created by ionized dopant atoms, making statements B and D true.
Step-by-step explanation:
The question asks which statements concerning the depletion zone of an unbiased p-n junction are true. The correct answers are:
- B. The width of the zone is dependent on the densities of the dopants (impurities).
- D. The electric field in the zone is produced by the ionized dopant atoms.
Step-by-step explanation:
An unbiased p-n junction creates a depletion region where no free charge carriers are present because they have recombined. The size of this region depends on the density of the dopants added to the semiconductor; thus, statement B is correct. The dopants are ionized, leaving behind fixed charges that create the electric field, making statement D true. Statement A is false because the width does vary with doping densities, and statement C is false because the electric field is not primarily due to electrons in the conduction band or holes in the valence band, but instead due to the ionized dopant atoms.