1. A vacant position in a crystal left by the absence of an electron; especially, a position in a semiconductor that acts as a carrier of positive electric charges.
2. In a semiconductor, the electron vacancy in the valence (combining power of atoms) band that occurs when an electron jumps the gap from the filled valence band to the empty conduction band.

It serves as a positive charge carrier, allowing electrons deeper in the band to move into the vacated area.

A valence is the combining power of atoms or groups measured by the number of electrons the atom or group will receive, give up, or share in forming a compound.

1. An electronic excitation, observed at low cryogenic temperatures in silicon and germanium, in which an electron-hole Fermi liquid is formed in an unstable condition.
2. A process by which a molecule is excited from a low-lying electronic state to a higher energy electronic state as observed in germanium and silicon at sufficiently low cryogenic temperatures.

It is associated with a liquid-gas phase transition of the charge carriers, and consists of regions of conducting electron-hole Fermi liquid coexisting with regions of insulating exciton gas.

A conduction electron in a conduction band and an accompanying electron hole in the valence band, that result when an electron jumps the gap in an intrinsic semiconductor.

A process in which a hole is combined again with an electron within a doped semiconductor (a process where impurities are added to a semiconductor), accompanied by a release of energy, normally in the form of radiation.