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The conduction band edge may also be indicated in an insulator, simply to demonstrate band bending effects. E V : The valence band edge likewise should be indicated in situations where electrons (or holes ) are transported through the top of the valence band such as in a p -type semiconductor .
In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level, and thus determine the electrical conductivity of the solid. In nonmetals, the valence band is the highest range of electron energies in which electrons are normally present at absolute zero temperature, while the conduction band is the lowest range of vacant electronic states.
Figure 1. (a) Shows an energy diagram of n-type semiconductor in contact with redox electrolyte at the left side (yellow), and with a metallic ohmic contact at the right side. E c is the conduction band edge energy, E v is the valence band energy of the semiconductor.
To understand how band structure changes relative to the Fermi level in real space, a band structure plot is often first simplified in the form of a band diagram. In a band diagram the vertical axis is energy while the horizontal axis represents real space. Horizontal lines represent energy levels, while blocks represent energy bands.
Based on the energy eigenvalues, conduction band are the high energy states (E>0) while valence bands are the low energy states (E<0). In some materials, for example, in graphene and zigzag graphene quantum dot, there exists the energy states having energy eigenvalues exactly equal to zero (E=0) besides the conduction and valence bands. These ...
The band gap (usually given the symbol ) gives the energy difference between the lower edge of the conduction band and the upper edge of the valence band. Each semiconductor has different electron affinity and band gap values. For semiconductor alloys it may be necessary to use Vegard's law to calculate these values.
In this article, the terms conduction-band referenced Fermi level or internal chemical potential are used to refer to ζ. Example of variations in conduction band edge E C in a band diagram of GaAs/AlGaAs heterojunction-based high-electron-mobility transistor.
Band edge diagram of a basic HEMT. Conduction band edge E C and Fermi level E F determine the electron density in the 2DEG. Quantized levels form in the triangular well (yellow region) and optimally only one of them lies below E F. Heterostructure corresponding to the band edge diagram above.