In solid state physics and related applied fields, the band gap, also called an energy gap or stop band, is a region where a particle or quasiparticle is forbidden from propagating. For insulators and semiconductors, the band gap generally refers to the energy difference between the top of the valence band and the bottom of the conduction band. Solid-state physics, the largest branch of condensed matter physics, is the study of rigid matter, or solids. ... In physics, a quasiparticle refers to a particle-like entity arising in certain systems of interacting particles. ... This article or section is in need of attention from an expert on the subject. ... A semiconductor is a solid whose electrical conductivity can be controlled over a wide range, either permanently or dynamically. ... In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature. ... In semiconductors and insulators, the conduction band is the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current. ...

In semiconductor physics

Semiconductor band structure.

In semiconductors and insulators, electrons are confined to a number of bands of energy, and forbidden from other regions. The term "band gap" refers to the energy difference between the top of the valence band and the bottom of the conduction band, where electrons are able to jump from one band to another. The other gaps are between bands are between a pair of filled or a pair of empty bands, which are unimportant to the properties of the semiconductor. Image File history File links Electronic_band_diagram. ... Image File history File links Electronic_band_diagram. ... In solid state physics, the electronic band structure (or simply band structure) of a solid describes ranges of energy that an electron is forbidden or allowed to have. ... e- redirects here. ... In solid state physics, the electronic band structure (or simply band structure) of a solid describes ranges of energy that an electron is forbidden or allowed to have. ... In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature. ... In semiconductors and insulators, the conduction band is the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current. ...

The conductivity of intrinsic semiconductors is strongly dependent on the band gap. The only available carriers for conduction are the electrons which have enough thermal energy to be excited across the band gap. Electrical conductivity is a measure of a materials ability to conduct an electric current. ... An intrinsic semiconductor, also called an undoped semiconductor or i-type semiconductor, is a pure semiconductor without any significant dopant species present. ...

Band gap engineering is the process of controlling or altering the band gap of a material by controlling the composition of certain semiconductor alloys, such as GaAlAs, InGaAs, and InAlAs. It is also possible to construct layered materials with alternating compositions by techniques like molecular beam epitaxy. These methods are exploited in the design of heterojunction bipolar transistors (HBTs), laser diodes and solar cells. An alloy is a combination, either in solution or compound, of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ... Molecular beam epitaxy, abbreviated MBE, is the deposition of one or more pure materials onto a single crystal wafer, one layer of atoms at a time, under ultra-high vacuum, forming a perfect crystal. ... The Heterojunction Bipolar Transistor (HBT) is an improvement of the bipolar junction transistor (BJT) that can handle signals of very high frequencies up to several hundred GHz. ... A packaged laser diode with penny for scale. ... A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ...

The distinction between semiconductors and insulators is a matter of convention. One approach is to consider semiconductors a type of insulator with a low band gap. Insulators with a higher band gap, usually greater than 3 eV, are not considered semiconductors and generally do not exhibit semiconductive behaviour under practical Band gap decreases with increasing temperature, in a process related to thermal expansion. Special purpose integrated circuits such as the DS1621 exploit this property to perform accurate temperature measurements. Band gap also depends on pressure. Bandgaps can be either direct or indirect bandgaps, depending on the band structure. In physics, thermal expansion is the tendency of matter to increase in volume or pressure when heated. ... An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ... In semiconductor physics, a direct bandgap means that the minimum of the conduction band lies directly above the maximum of the valence band in momentum space. ... In semiconductor physics, an indirect bandgap is a bandgap in which the minimum energy in the conduction band is shifted by a k-vector, which is determined by the materials crystal structure. ... In solid state physics, the electronic band structure, or simply band structure, refers to the dispersion relation (the relation between energy versus momentum) of electrons in a crystal. ...

Mathematical interpretation

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The probability that a state of energy, E₀, will be occupied by an electron is derived from Fermi-Dirac statistics. An approximation, called the Boltzmann approximation, is valid if the energy of the state E₀ > > E_F, where E_F is the Fermi energy. The Boltzman approximation is given by: Image File history File links Fairytale_waring. ... This Manual of Style has the simple purpose of making things easy to read by following a consistent format — it is a style guide. ... Fermi-Dirac distribution as a function of ε/μ plotted for 4 different temperatures. ... In physics and Fermi-Dirac statistics, the Fermi energy (EF) of a system of non-interacting fermions is the smallest possible increase in the ground state energy when exactly one particle is added to the system. ...

where:

e is the exponential function

E_g is the band gap energy

k is Boltzmann's constant

T is temperature

Conductivity is undesirable, and larger band gap materials give better performance. In infrared photodiodes, a small band gap semiconductor is used to allow detection of low-energy photons. The exponential function is one of the most important functions in mathematics. ... The Boltzmann constant (k or kB) is the physical constant relating temperature to energy. ... Fig. ... Image of two girls in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... A photodiode Photodiode closeup A photodiode is a semiconductor diode that functions as a photodetector. ...

In photonics and phononics