What is characterized by the increased conductivity of an illuminated semiconductor junction?

The phenomenon characterized by the increased conductivity of an illuminated semiconductor junction is known as the photoconductive effect. When a semiconductor material, such as silicon, is exposed to light, photons can excite electrons from the valence band to the conduction band. This excitation increases the number of free charge carriers (electrons and holes), enhancing the material's conductivity.

This process is fundamental to the operation of devices like photodetectors and solar cells, where the absorption of light directly impacts the electrical properties of the semiconductor, allowing it to conduct electricity more efficiently. This effect is particularly useful in applications that rely on light to influence the electronic properties of materials, leading to the development of various optoelectronic devices.

The other options do not accurately describe this process. Semiconductor degradation refers to the deterioration of material properties over time, capacitive reactance deals with the opposition to changes in voltage in capacitors, and resistive coupling relates to connecting circuits through resistive elements, none of which directly involve the increased conductivity of a semiconductor due to illumination.