Semiconductors and Energy Bands

Semiconductors are materials that have electrical conductivity between that of a conductor and an insulator. They are used in a variety of electronic devices such as computers, cell phones, and solar cells. The electrical properties of semiconductors are determined by their energy bands.

What are Energy Bands?

Energy bands are ranges of energy levels that electrons in a material can occupy. In a solid, the electrons are restricted to certain energy levels due to the presence of the atoms and their interactions with each other. The energy bands in a solid are divided into two main categories: the valence band and the conduction band.

Valence Band

The valence band is the range of energy levels that electrons occupy when they are bound to atoms in the material. These electrons are not free to move around and conduct electricity, so the material is an insulator.

Conduction Band

The conduction band is the range of energy levels that electrons can occupy when they are not bound to atoms in the material. Electrons in the conduction band are free to move around and conduct electricity, so the material is a conductor.

Energy Gap

The energy gap is the separation in energy between the valence band and the conduction band. In an insulator, the energy gap is large, so the electrons in the valence band cannot easily jump to the conduction band and conduct electricity. In a conductor, the energy gap is small or zero, so the electrons in the valence band can easily jump to the conduction band and conduct electricity.

Semiconductors

In a semiconductor, the energy gap is small, typically around 1 electron volt (eV). This means that the electrons in the valence band can easily jump to the conduction band with a small amount of energy, such as heat or light. This makes semiconductors useful in electronic devices that require precise control of electrical conductivity, such as transistors and diodes.

Conclusion

In conclusion, the separation between the conduction band and the valence band in a semiconductor is of the order of 1 eV. This small energy gap allows electrons to easily jump from the valence band to the conduction band, making semiconductors useful in electronic devices.