Semiconductor

In an unbiased semiconductor diode, the depletion region is formed where the free electrons and holes recombine, resulting in a region with no free charge carriers. This is a key characteristic of the depletion region in a p-n junction diode.

In copper, the valence band and conduction band overlap, allowing electrons to flow freely and making copper an excellent conductor. In contrast, in materials like silicon and germanium, there is a gap between the valence and conduction bands, making them semiconductors.