Energy vs. momentum for a semiconductor with a direct band gap, showing that an electron can shift from the lowest potential in the conduction band (green) to the highest potential in the valence band (red) without a change in momentum.

In semiconductor physics, a direct bandgap means that the minimum energy of the conduction band lies directly above the maximum energy of the valence band in momentum space. A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. In Solid state physics and related applied fields a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states In the Physics field of Semiconductors and insulators the conduction band is the range of Electron Energy, higher than that of the In Solids the valence band is the highest range of Electron energies where electrons are normally present at Absolute zero. The Momentum space associated with a particle is a vector space in which every point {k_x k_y k_z} corresponds to a possible value of the Momentum vector \vec{k} In a direct bandgap semiconductor, electrons at the conduction-band minimum can combine directly with holes at the valence band maximum, while conserving momentum. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J An electron hole is the conceptual and mathematical Opposite of an Electron, useful in the study of Physics and Chemistry. The energy of the recombination across the bandgap will be emitted in the form of a photon of light. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena This is radiative recombination, also called spontaneous emission. Spontaneous emission is the process by which a light source such as an Atom, Molecule, Nanocrystal or nucleus in an Excited state In indirect bandgap semiconductors such as crystalline silicon, the momentum of the conduction band minimum and valence band maximum are not the same, so a direct transition across the bandgap does not conserve momentum and is forbidden. Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Recombination occurs with the mediation of a third body, such as a phonon or a crystallographic defect, which allows for conservation of momentum. In Physics, a phonon is a quantized mode of vibration occurring in a rigid crystal lattice, such as the Atomic lattice of a Solid Crystalline solids have a very regular atomic structure that is the local positions of atoms with respect to each other are repeated at the atomic scale These recombinations will often release the bandgap energy as phonons, instead of photons, and thus do not emit light. As such, light emission from indirect semiconductors is very inefficient and weak. This is a list of sources of Light, including both natural and artificial sources and both processes and devices. There are new techniques to improve the light emission by indirect semiconductors. See indirect bandgap for an explanation. In Semiconductor Physics, an indirect bandgap is a Bandgap in which the minimum energy in the Conduction band is shifted by a

The prime example of a direct bandgap semiconductor is gallium arsenide—a material commonly used in laser diodes. Gallium arsenide ( GaAs) is a compound of two elements Gallium and Arsenic. A laser diode is a Laser where the active medium is a Semiconductor similar to that found in a Light-emitting diode.

See indirect bandgap for an explanation of the connection between bandgap offset and light emission. In Semiconductor Physics, an indirect bandgap is a Bandgap in which the minimum energy in the Conduction band is shifted by a