What does it mean when a substance is said to have semiconductor properties?

When a substance is described as having semiconductor properties, it means that it can conduct electricity under certain conditions. This unique characteristic arises from the material's electronic structure, which allows it to behave differently than conductors and insulators. Semiconductors can conduct electrical current when energy (such as heat or light) is applied to them, which excites the electrons and allows them to move freely.

For example, silicon, one of the most widely used semiconductor materials, can effectively conduct electricity when doped with certain impurities, enhancing its ability to facilitate electrical current under specific conditions. This is fundamental in many electronic devices, such as diodes and transistors, where the control of electrical conductivity is essential.

The other options do not accurately reflect the nature of semiconductors. While conductors allow electricity to flow freely at all times and insulators do not conduct electricity at all (regardless of temperature), semiconductors fall into a middle category where their conductivity can be manipulated by factors like temperature, doping, and light exposure. So, the statement that best describes semiconductor properties is that they can conduct electricity under certain conditions.