What is a band gap?
Q: What is a band gap?
A: A band gap, also called a bandgap or energy gap, is an energy range in a solid where no electron states can exist.
Q: What does the term refer to in solid-state physics and chemistry?
A: The term refers to the energy difference (in electron volts) between the top of the valence band and the bottom of the conduction band. This is also known as the energy needed to free an outer shell electron from its orbit about the nucleus to become a mobile charge carrier.
Q: How does it affect electrical conductivity?
A: The band gap is a major factor determining electrical conductivity of a solid. Substances with large band gaps are generally insulators, those with smaller band gaps are semiconductors. Conductors either have very small band gaps or no band gap if the energy levels of valence and conduction bands overlap.
Q: How do electrons move within solids?
A: Electrons are able to move freely within solid materials when they become mobile charge carriers after being freed from their orbits around nuclei.
Q: What happens when electrons reach higher energies?
A: When electrons reach higher energies, they can jump across the energy barrier created by the band gap and become free electrons that can move freely within a solid material.
Q: Are all solids insulators or semiconductors?
A: Not all solids are insulators or semiconductors; some may be conductors if their valence and conduction bands overlap, resulting in very small or no band gaps at all.
