Silicon SemiconductorPublished on 24/2/2012 and last updated on 1/11/2018
When an electrical field is applied they will move and become conduction electrons. That means that the silicon has a negative resistance temperature coefficient. Pure silicon has covalent bonds energy of 1.1 eV. That means how much energy it takes to free the valence electrons in the crystal structure. Pure monocrystalline silicon is used as a wafer and mechanical support for integral circuits. The pure silicon poorly conducts the electrical energy. The silicon is doped with different impurities to increase the conductivity level of the material. The impurities have added the extra energy levels, and an energy band gap becomes extended. Semiconductors with wide band gap imply materials with the band gap energy above 2 eV. Those semiconductors are suitable for high power electronics, high temperature, and high operation frequency conditions. The Silicon Carbide (SiC) gives the best results in commercial electronic components production. It has band gap energy of 3.03 eV.
The silicon with added impurities can become N-type semiconductor or P-type semiconductor. If the impurity with five valence electrons donor (Nitrogen-N, Phosphorus-P, Arsenic-As, Antimony-Sb, Bismuth- Bi) is added to the pure tetravalent silicon, the four impurity electrons will be covalently tied up with four neighbourly Si atoms and forming covalent bonds. The fifth electron remains free and thanks to the thermal energy it chaotically moves in the crystal lattice. Free electrons conduct electricity if an external electric field exists. The P-type semiconductor is formed by adding trivalent impurity- acceptor (indium-In, boron-B, aluminum-Al, and gallium-Ga) to the pure tetravalent silicon the covalent bonds will be formed with three Si atoms. An empty space is known as a hole. The formed hole is free to move in the crystal lattice. In this case, the positively charged holes will conduct electricity.