Conduction And Valence Band In Semiconductors

A specific amount of energy separates the two distinct energy levels of the conduction band and valence band. The main distinction between the valence band and the conduction band is that the valence band describes the energy level of electrons in an atomic structure’s valence shell. On the other hand, a conduction band contains the electrons responsible for conduction. The conduction band and the valence band intersect in metallic conductors. At sufficiently low temperatures, the conduction band in semiconductors and inductors is devoid of electrons. Thermal excitation of electrons from a lower energy band or impurity atoms in the crystal produces conduction electrons.

Band Theory

According to the band theory, semiconductors will operate as insulators at absolute zero. The metal would operate as a semiconductor above this temperature while remaining below the solid’s melting point. The fully occupied valence band and the unoccupied conduction band classify semiconductors. Because of the tiny band gap between these two bands, exciting electrons from the valence to the conduction band require energy. 

Conduction Band

In a crystalline material that is partially filled with electrons, the conduction band is a delocalized band of energy levels. These electrons are responsible for electrical conductivity and have high mobility. When an atom is energized, electrons can jump to a band of electron orbitals called the conduction band. These electrons leave the valence band and jump to the conduction band. These electrons have enough energy to flow freely inside a material while in the conduction band. An electric current is created as a result of this movement.

The bandgap is the energy difference between the valence band’s highest energy level energy state and the conduction band’s lowest occupied energy state. The bandgap is a measurement of a material’s electrical conductivity. The two bands overlap, just like in conductors, and electrons in the lower energy band can easily travel to the conduction band. However, external energy is required to release the valence electrons because there is a substantial energy gap between the two bands in semiconductors. However, the bandgap is quite big in insulators, requiring a lot of energy to make the valence electron a free electron.

Valence Band

It is generally described as the energy band that consists of valence band electrons in an atomic structure’s outermost shell. When given enough energy, these valence electrons become free electrons and travel to the conduction band, resulting in conductivity. In the energy level diagram, it is at a lower energy level than the conduction band and is abbreviated as the valence band. The forbidden energy gap is the amount of energy that separates these two bands. This energy gap is determined by the type of material, which is either a conductor, an insulator, or a semiconductor. The valence and conduction bands are nearest to the Fermi level in solid-state physics and influence the solid’s electrical conductivity. The valence band is the largest range of electron energies in which electrons are generally found at zero temperature in semiconductors.

Valence Band vs. Conduction Band Main Differences

When an atom is stimulated, electrons can leap out of the valence band, made up of electron bands. However, in a crystalline material that is partially filled with electrons, the conduction band is a delocalized band of energy levels. Following are the key difference between the Conduction band and Valence band:

1. Below the Fermi energy level, there is a valence band. In the energy band diagram, the conduction band is present above the Fermi level.
2. Electrons in the valence band move out when external stimulation is applied. The electrons, however, shift into the conduction band due to external energy.
3. The density of electrons in the valence band is higher than in the conduction band.
4. The valence band is frequently partially or filled at ambient temperature. At room temperature, the conduction band is usually vacant or partially replaced.
5. The valence band has a lower energy level than the conduction band, which has a larger energy level.
6. The nucleus exerts a strong push on the electrons in the valence band. On the other hand, the nucleus exerts a weak or non-existent force on the electrons in the conduction band.

Conclusion

Valence electrons are the electrons that are found within the outer shell. These electrons are made up of a series of energy levels that make up the valence band.  At normal temperature, the valence electrons are loosely linked to the nucleus. Some valence electron electrons will be able to depart the band freely. These free electrons, also known as conduction electrons, will conduct current flow within a conductor. The conduction band, which includes electrons, is named after the occupied energy of this band.