What is the energy band theory in semiconductors?

The energy band theory explains the behaviour of electrons in semiconductors and their ability to conduct electricity.

In a semiconductor, the valence band is filled with electrons and the conduction band is empty. When an external energy source is applied, such as heat or light, electrons can be excited from the valence band to the conduction band, creating a flow of current. This is the basis for the operation of many electronic devices, such as transistors and diodes.

The energy band theory also explains the concept of doping, where impurities are intentionally added to a semiconductor to alter its electrical properties. Adding impurities with extra electrons, such as phosphorus, creates an n-type semiconductor with excess electrons in the conduction band. Adding impurities with missing electrons, such as boron, creates a p-type semiconductor with holes in the valence band. When an n-type and p-type semiconductor are brought together, they form a p-n junction, which is the basis for many electronic devices, such as solar cells and LEDs.

Overall, the energy band theory is a fundamental concept in the field of semiconductor physics and is essential for understanding the behaviour of electronic devices.