Magnetic Materials L

ELECTRICAL PROPERTIES OF SEMICONDUCTORS

          It is a known fact that electrons revolve round the nucleus in definite circular orbits under the influence of short range attractive forces called nuclear forces.   If the potentiality of electron is   strong enough to overcome this force of attraction we can designate them as conductors, on the other hand if the energy of electron is least to overcome the nuclear short range forces such materials are called as insulators or in simple words we can say that materials which reveal intermediate behaviour in between conductors and insulators are termed as semiconductors. At   Ok semiconductors behave themselves as insulators, because it is general pedagogy that all electrons at Ok will be localised in the valence band. As a result of this   electrons cannot jump from valence band to conduction band because they are tightly bounded themselves, even after the application of higher temperatures only few electrons will try to jump to conduction band. So on the whole some of the insulators at OK will behave as a conductor at room temperature.
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The band formed by valence electrons is valence band   it is always fulfilled but can never be empty, on the other hand band formed by conduction electrons will serve as conduction band. For an electron to behave as an conductor there should be an unfilled electron in its configuration, the conduction band may be partially filled or empty.   Since energy band is nothing but the packet of energy levels, they may be degenerative or non degenerative energy levels depending   on the nature of atom. If the atom is in isolated form the energy levels are non degenerative   and degenerative in the sense if it is unisolated form. The gap between conduction band and valence band is called forbidden band where the electron cannot stay less than a nanosecond of time. The phenomenon of semiconductors can be best understood   with the help of quantam mechanics which specifies the motion of...