At present we can find chips in every application, even in space application. And silicon (Si) is widely used material for manufacturing the chips. Semiconductors materials are used mostly in chips. Based on Energy Band gaps the metals are classified into
A band gap is the distance between the valence band of electrons and the conduction band of electrons. A band gap is minimum energy required to excite an electron to conduction band from a valence band
Conduction band is the band of orbitals that are high in energy and are generally empty at room temperature. In reference to conductivity, it is the band which accepts the electrons
Valence Band is the band occupied with molecular orbitals which are lower in energy. When there is temperature raise, the electron will jump from the valence band to conduction band, making the materials conductive
Fermi Level is defined as highest occupied molecular orbital in valence band at 0 k. The Fermi level lies between the valence band and conduction band because electrons will eventually occupy the low energy states at room temperature. Fermi level can be considered as sea of electrons above which no electrons will exits. Fermi level changes as the solids are warmed and electrons are removed or added to orbitals
In conductors the valence band and conduction bands are overlapped. This overlap causes the valence electrons to move freely in conduction band which results in conduction. Metals, living beings are few good conductor materials. This materials offers less resistance to flow of electrons.
There is no band gap in conductors and electrons are free to move to conduction band.
In Insulators the conduction band and valence band are separated with large band gap. This prevents the electrons movement between the valence band and conduction band. And there will be no conductivity. Wood, plastic, glass are few of the insulating materials. This material offer more resistance to flow of electrons.
In the semiconductors the band gap energy is small, as a result with small amount of heat or energy electrons get excited and jumps from the valence band to conduction band. There will be conduction of electricity and with small amount of doping conductivity of materials will be increased. In this material we can control the flow of electrons.
There are two types of semiconductors.
- N-type Semiconductor electrons are majority carrier for electricity and hole are minority carriers
- P-type Semiconductor holes are majority carrier for electricity and electrons are minority carriers