What characterizes p-type semiconductors?

P-type semiconductors are characterized by the presence of "holes" that facilitate positive charge flow. This occurs when a semiconductor material, typically silicon, is doped with elements that have fewer valence electrons than silicon, such as boron. These dopants create empty electronic states, or "holes," in the crystal lattice, which can be thought of as positive charge carriers.

In a p-type semiconductor, when an electron from the valence band of the semiconductor moves to fill a hole, it creates a new hole in the location that the electron moved from. This movement of holes allows for the conduction of electricity, as these holes can effectively allow for the flow of charge in a direction opposite to that of electrons. Therefore, the characteristic feature of p-type semiconductors is primarily tied to the generation and movement of these holes, making positive charge flow possible.

The other options do not accurately define p-type semiconductors. Donor impurities are associated with n-type semiconductors, purely conductive materials do not exist in the realm of semiconductors as they usually involve some resistance, and enhancing electron mobility pertains more to n-type than p-type semiconductors.