Physics - Semiconductors Question with Solution | TestHub

In solid-state physics, materials are classified into conductors, insulators, and semiconductors based on the size of the forbidden energy gap ($E_g$) between the valence band and the conduction band.

For conductors, the valence band and conduction band overlap, so the band gap is zero.

For insulators, the forbidden energy gap is very large, typically greater than $3$ eV to $5$ eV, making it extremely difficult for electrons to jump to the conduction band.

For semiconductors, the forbidden energy gap is small but non-zero, usually around $1$ eV or less. For example, the band gap for Silicon is approximately $1.1$ eV and for Germanium is approximately $0.7$ eV at room temperature.

Therefore, the band gap in semiconductors is $1$ eV or less but greater than zero.

Answer: $1\text{eV}$ or less but greater than zero.