The energy band theory provides insight into the behavior of electrons in semiconductors and their capacity to conduct electricity.

In a semiconductor, the valence band is typically filled with electrons, while the conduction band remains empty. When an external energy source, such as heat or light, is applied, electrons can gain sufficient energy to be excited from the valence band to the conduction band. This process generates a flow of electric current, which is fundamental to the operation of various electronic devices, including transistors and diodes.

Moreover, energy band theory elucidates the concept of doping, where intentional impurities are introduced into a semiconductor to modify its electrical characteristics. For instance, adding impurities that have extra electrons, such as phosphorus, results in the formation of an n-type semiconductor, characterized by an abundance of electrons in the conduction band. Conversely, when impurities with fewer electrons, like boron, are introduced, a p-type semiconductor is created, featuring “holes” in the valence band.

When n-type and p-type semiconductors are combined, they create a p-n junction, which is crucial for the functionality of numerous electronic devices, such as solar cells and light-emitting diodes (LEDs).

In summary, energy band theory is a fundamental principle in semiconductor physics, essential for understanding the behavior and operation of electronic devices.