What are holes in the semiconductor



As Defect electron, Electron vacancy or hole is the name of the (virtual) positive mobile charge carrier in semiconductors.

It arises, among other things, when high-purity semiconductors (silicon, germanium, gallium arsenide, etc.) are deliberately contaminated with certain trivalent or pentavalent elements (mostly boron or aluminum for Si or Ge), i.e. they are incorporated into the crystal lattice as foreign atoms through diffusion or ion implantation (see doping). However, conduction through defect electrons can also arise through intrinsic conduction in the undoped crystal, ie. for example, breaking a covalent bond between two Si atoms creates a gap. This gap (usually called "hole" in physics) can move in the same way without a lack of electrons having to be caused by foreign atoms: An adjacent electron can now jump to this free point in the crystal structure, something that comes from outside looks like a positively charged hole is moving (comparable to an air bubble in a liquid). In the band model, one speaks of a transition of the electron from the valence band to the conduction band (or the defect electron from the conduction band to the valence band), which can be caused, for example, by thermal excitation.

An important characteristic variable of semiconductors is the charge carrier mobility. However, this is not automatically the same for electrons and holes, but depends on the material, doping, temperature, etc., for example.

Examples from the application

The generation of electron-hole pairs by optical excitation and subsequent separation of the same at the p-n junction is used in solar cells to convert light into electrical energy.

See also

Category: Solid State Physics