Which of the following best describes a semiconductor material?

Semiconductor Materials

A semiconductor is a type of material that has electrical conductivity between that of a conductor (like copper) and an insulator (like glass). The conductivity of semiconductors can be controlled by external factors such as temperature, light, or the addition of impurities (a process known as doping).

Characteristics of Semiconductor Materials:

• They have a band gap, which is an energy range in a solid where no electron states can exist. The band gap in semiconductors is smaller than in insulators but larger than in conductors.
• Semiconductors can be intrinsic or extrinsic:
  • Intrinsic Semiconductors: Pure semiconductors without any significant impurities. Examples include silicon (Si) and germanium (Ge).
  • Extrinsic Semiconductors: Semiconductors that have been doped with impurities to improve their electrical conductivity. Doping introduces free charge carriers (electrons or holes).
• They exhibit a phenomenon called "negative temperature coefficient," where their resistance decreases as the temperature increases.

Applications of Semiconductors:

• Used extensively in electronic devices such as diodes, transistors, and integrated circuits.
• Play a crucial role in solar cells, LEDs, and laser diodes.
• Essential for the functioning of computers, smartphones, and other modern communication devices.

Correct Option Analysis:

The correct option is:

Option 4: A material that can conduct electricity under certain conditions but not others.

This option accurately describes the behavior of semiconductor materials. Semiconductors are unique because they can either conduct or insulate electricity depending on external factors such as temperature, light, or doping. This property is fundamental to their use in modern electronics.