Forbidden Band


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forbidden band

[fər¦bid·ən ′band]
(solid-state physics)
A range of unallowed energy levels for an electron in a solid.

Forbidden Band

 

a region of values of energy that electrons in an ideal crystal (without defects) cannot have. In semiconductors the forbidden band separating the valence band and the conduction band is usually considered. In this case the energy difference between the lower level (bottom) of the conduction band and the upper level (ceiling) of the valence band is called the width of the forbidden band.

References in periodicals archive ?
The empty N 2p state mainly contributes to the impurity energy levels in the forbidden band. The Si 3s electrons appear in the range (-7)-(-6.5) eV in the Sis(Ti) model (Figure 3(b)).
The N-doped Ti[O.sub.2] showed a redshifted intrinsic absorption edge due to the band gap narrowing and the absorption had extended into the visible and infrared (IR) regions, owing also to the N 2p impurity energy level that occurs in the forbidden band mentioned previously in Section 3.3.
Note that, as the emitted frequency of the QPAB is detuned deep inside the forbidden band region ([delta]/[beta] = -5 and -10), the energy-relaxation rates exhibit negative values in the initial period of relaxation.
The frequency range of this forbidden band is tunable through the array parameters and applying external flux.
For the absorption of photons by this band, the energy of the photons representing the region of the width of the forbidden band can be calculated using
It is more important that the transmission band begins to form; forbidden band can clearly be seen in the transmission spectra from Figure 3(b).
Initial results show that this structure has a number of unexpected features, including an extra forbidden band.
There is increasing interest into deposition of ternary derivative materials due to their potential for designing and tailoring not only the lattice parameters, but also the forbidden band gap energy [E.sub.g], by means of the growth parameters [1, 2].
In such a case the allowed and forbidden bands are clearly separated.
The quadrupole interaction is a just theoretical artifact so far, he admits, but it explains the appearance of forbidden bands arising in a great number of experiments on symmetrical molecules with surface enhanced Raman scattering (SERS).
Photonic crystals are analogous to semiconductors, in that both create forbidden bands: regions in the energy spectrum where information carriers (electrons/holes or photons) cannot exist.
Such forbidden bands are called Photonic Band Gaps (PBG) which is similar to the electronic band gaps for electrons in semiconductors [8,9].