What Is a Conduction Band?

The conduction band is the energy space formed by free electrons. That is, the energy range of freely moving electrons in a solid structure.

The conduction band is defined by

For an undoped intrinsic semiconductor, the electrons in the conduction band are formed by the transition of the electrons (valence electrons) in an energy band below it (that is, the valence band), which generates electrons (also generates holes) -Another kind of carrier in semiconductors), called intrinsic excitation . In the process of intrinsic excitation, electrons and holes are generated in pairs, so there is always "electron concentration = hole concentration". This is actually the characteristic of an intrinsic semiconductor, so it can be said that any semiconductor with the same carrier concentration is an intrinsic semiconductor. This means that not only undoped semiconductors are intrinsic semiconductors, but also doped semiconductors, which can also be transformed into intrinsic semiconductors under certain conditions, such as at high temperatures.

The energy of the valence band is lower than the conduction band, and it is also composed of many quasi-continuous energy levels. However, many electrons (valence electrons) in the valence band cannot conduct electricity, and a small number of valence electron vacancies- holes can conduct electricity, so holes are called carriers. The lowest energy of a holepotential energy, is the top of the valence band, and usually the hole is near the top of the valence band.

The energy difference between the valence band top and the conduction band bottom is the so-called semiconductor forbidden band width. This is the minimum average energy required to produce an intrinsic excitation. This is one of the most important characteristic parameters of semiconductors.

For doped semiconductors, electrons and holes are mostly provided by impurities. Impurities that can provide electrons are called donors ; impurities that can provide holes are called acceptors . The energy level of the donor is in the forbidden band near the bottom of the conduction band; the energy level of the acceptor is in the forbidden band near the top of the valence band. ^[1]