In solid-state physics, the electronic band structure (or simply band structure) of a solid describes the range of energy levels that electrons may have within it, as well as the ranges of energy that they may not have (called band gaps or forbidden bands).

Within any given material there are two distinct energy bands in which electrons may exist. These two energy bands are valence energy band (or valence band) and conduction energy band (or conduction band) and are separated by an energy gap in which no electron can normally exist, as illustrated in Fig. 6.4.

Similarly, energy bands can also result from overlapping $p$ and $d$ orbitals. The electronic states (orbitals) within an energy band are filled progressively by pairs of electrons in the same way that the orbitals of an atom were filled in accordance with the Pauli principle.

Band theory models the behaviour of electrons in solids by postulating the existence of energy bands. It successfully uses a material’s band structure to explain the many physical properties of solids.

Metals: (i) For metals, the valence band is completely filled and the conduction band can have two possibilities—either it is partially filled with an extremely small energy gap between the valence and conduction bands or it is empty, with the two bands overlapping each other as shown below:

Semiconductors have a small energy gap between the valence band and the conduction band. Electrons can make the jump up to the conduction band, but not with the same ease as they do in conductors. There are two different kinds of semiconductors: intrinsic and extrinsic .

The energy band is a very important concept in metal and semiconductor engineering. Metals become conductors that conduct electricity well because electrons can move freely around them through energy bands.

Energy Bands. The energy spectrum result from solving the Equation (1) have large number of solutions, giving discrete energies \(E_{1,\mathbf{k}}\), \(E_{2,\mathbf{k}}\) etc., for each value of k and is shown in Figure \(\PageIndex{4}\).

Jul 12, 2023 · Bonding in metals and semiconductors can be described using band theory, in which a set of molecular orbitals is generated that extends throughout the solid. The primary learning objective of this Module is to describe the electrical properties of solid using band theory.

Feb 22, 2024 · Gain a comprehensive understanding of energy bands and how they form in semiconductors. Explore the significance of band gaps in differentiating conductors, semiconductors, and insulators, and discover how doping …