A material is called semiconductor if
(a) it conducts electricity moderately.
(b) Its forbidden band gap is very small (≈ 1 eV)
(c) Its σ /w ε is neither small nor large.
Some typical semiconductor materials are: Germanium, Graphite and Silicon.
Semiconductors are utilized in bipolar junction, diodes, transistor construction, JFETs, MOSFTs, UJTs and SCRs, amplifiers, oscillators, microwave devices, etc.
Some of the important properties of semiconductors are given below:
1. Conductivity of a semiconductor lies among that of conductors and insulators.
2. Pure semiconductor act like insulator at low resistance.
3. Its conductivity enhance with increase in temperature.
4. Semiconductors have always 4 electrons in its outer orbit.
5. Concentration of free electron lies between that of and insulators and conductors.
So far, you have learned about the various properties and characteristics of materials which are classified as insulators, conductors and semiconductors. In next sections you shall learn about the properties like, inductance, resistance and capacitance of materials.