Band Theory of Semiconductors is one of the important concepts in solid-state physics, which enables one to study and understand the motions of electrons in different materials, which lead to the conduction in some materials and not the conduction in certain others. Band Theory explains the distribution of electrons into the various energy levels or bands in a solid. The interaction of many atoms in a crystal lattice forms these energy bands. The behavior of electrons within these bands determines a conductance conduction.
Valence Band
In solid-state physics, conductive type indeterminate properties occurrence of solid has to define the valence band and conduction band as those rows closest to the Fermi level in the crystals. Thus, it becomes the bands, which determine the electrical conductivity of solids. The band at absolute zero in electrical insulators and semiconductors is the highest range of electron energies in which electrons are normally found.
So, fourteen electrons are present in silicon as an atom. They all lined up in ground state electron configuration [Ne]3s23p2. In the case of four, two of these are valence and lie in 3s and two in 3p orbitals. It is meaningless in metals to speak of the valence and conduction bands, since conduction will take place in one or another of the partially filled bands, both identified with the properties of the valence and conduction bands.
Conduction band
The valence and conduction bands are the two prime bands in a solid with reference to the Fermi level. They play an important role in determining the electrical conductivity of the solid. The conduction band represents the lowest range of unoccupied electronic states. It is in a solid material used as an electrical insulator or semiconductor. A plot of electronic band structure defines the valence and conduction bands as lying below and above the Fermi level, respectively. In semiconductors, electrons can rise to the conduction band if they are able to excite them. Usually via ionizing radiation (that is, they must acquire energy higher than Egap).
For example, diamond is a wide-band gap semiconductor (Egap = 5.47 eV). It has vast potential as a material for electronic devices. The requirement for operating the detector at cryogenic temperatures is realized in of germanium due to its small band gap energy (Egap = 0.67 eV).
Use in Semiconductors
There occurs some conduction in semiconductors. This is because some electrons get sufficient thermal energy to break their bonds at the valence band and jump into the conduction band. Once in the conduction band, they can conduct currents, or the hole chewed by an electron in the valence band that enabled that electron to jump from it. Whereas the hole itself is left empty, creating a place for the electrons in the valence band to have more freedom. Semiconductors overcome by external stimuli such as temperature or doping. They include silicon (Si), germanium (Ge), gallium arsenide (GaAs), and indium phosphide (InP). Doping is the method of introducing small quantities of other elements. Usually into a semiconductor to modify its electrical characteristics.
Band Theory of Semiconductors is one of the most important things to discuss for better understanding in electronics.
