What process enhances the conductivity of a semiconductor?

Doping is the process used to enhance the conductivity of a semiconductor. This technique involves the intentional introduction of impurity atoms into the semiconductor material, which modifies its electrical properties. Semiconductors in their pure form, known as intrinsic semiconductors, have relatively low conductivity. When doped with specific elements, such as phosphorus or boron (for n-type and p-type doping respectively), extra charge carriers (electrons or holes) are introduced into the material. This increases the number of charge carriers available for electrical conduction, thereby significantly increasing the conductivity of the semiconductor.

The other processes listed do not improve semiconductor conductivity in the same manner. Ionization refers to the process of gaining or losing electrons to form charged particles, which is not a targeted method for enhancing conductivity in semiconductors. Evaporation generally describes a phase transition from a liquid to a gas, and while it can be part of semiconductor fabrication processes, it does not directly increase conductivity. Melting involves changing a solid into a liquid state, which is also unrelated to the enhancement of electrical properties in solid-state materials. Thus, doping is fundamental in the design and optimization of semiconductor devices used in electronics.