in solid-state physics, the name given to a missing electron in certain metals and semiconductors (semiconductor). A missing electron is the same as an added positive electric charge, and hence holes behave like positive charges, moving opposite to electrons under the effect of an electric field. Holes affect the electrical, optical, and thermal properties of the solid. Along with electrons, they play a critical role in modern digital technology when they are deliberately introduced into semiconductors.

According to the band theory of solids, electrons within a solid have energies only at certain discrete levels that combine into groups or bands. The valence band contains electrons that are bound into the atomic structure of the material (see valence electron), whereas the conduction band contains electrons that are free to move.

The band structure of a semiconductor (that is, the distribution of its electrons) can be changed by the process called doping, in which impurities, known as dopants (dopant), are added to the material. In silicon, the semiconductor used in computer chips, the addition of a small amount of arsenic increases the number of electrons because each arsenic atom contains one more electron than the silicon atom it replaces. Such a material is said to be -type for its excess negative charges. -type (for excess positive charges) silicon results if the dopant is boron, which contains one electron fewer than a silicon atom. Each added boron atom creates a deficiency of one electron; deficiencies are known as positive holes and, like excess electrons, can transport current.

Electrons and holes both move when a voltage is applied, and both contribute to the electrical properties of a doped semiconductor. N- and p-type semiconductors can be combined to form field-effect transistors (integrated circuit), a basic component in integrated circuits (integrated circuit).