An energy band diagram in semiconductors is a graphical representation of the energy levels of electrons in a semiconductor material. It shows the energy bands, or allowed energy levels, for both the valence band (occupied by electrons) and the conduction band (unoccupied by electrons). The energy band diagram helps to explain the electrical properties of semiconductors.
The energy band diagram for conductors has overlapping valence and conduction bands, allowing electrons to easily move between the two. Insulators have a large band gap, with a completely filled valence band and an empty conduction band. Semiconductors have a smaller band gap compared to insulators, allowing some electrons to jump from the valence band to the conduction band when energy is supplied, making them partially conductive.
The band gap in a semiconductor energy band diagram is the energy difference between the valence band and the conduction band. This gap represents the minimum amount of energy required to excite an electron from the valence band to the conduction band, making the material conductive. The size of the band gap determines the electrical properties of a semiconductor.
Doping, the intentional addition of impurities, can change the energy band diagram in semiconductors. N-type doping adds extra electrons to the conduction band, while P-type doping creates extra holes (empty spaces) in the valence band. This results in a shift in the energy levels and can decrease the band gap, making the material more conductive.
An intrinsic semiconductor is a pure material with no intentional doping, while an extrinsic semiconductor has been intentionally doped. In an energy band diagram, an intrinsic semiconductor will have a small band gap and a symmetric distribution of electrons and holes. An extrinsic semiconductor will have a lower or higher band gap depending on the type of doping and a non-symmetric distribution of electrons and holes.