Temperature (t) dependence of resistivity (p) for a typical semiconductor is best shown by
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The resistivity of materials depend on the temperature. ρt = ρ0 [1 + α (T – T0) is the equation that shows the relation between the temperature and the resistivity of a material. In the equation ρ0 is the resistivity at a standard temperature, ρt is the resistivity at t0 C, T0 is the reference temperature and α is the temperature co – efficient of resistivity.
*Variation of semiconductor*=
Silicon is a semiconductor. In semiconductors the forbidden gap between the conduction band and the valence band is small. At 0K, the valence band is completely filled and the conduction band may be empty. But when a small amount of energy is applied, the electrons easily moves to the conduction band. Silicon is an example for semiconductor. Under normal circumstances silicon act as a poor conductor. Each silicon atom is bonded to 4 other silicon atoms. The bonds between these atoms are co valent bonds where the electrons are in fixed positons. So at 0K, the electrons does not move within the lattice structure.
When the temperature in increased the forbidden gap between the two bands becomes very less and the electrons move from the valence band to the conduction band. Thus some electrons from the co valent bonds between the Si atoms are free to move within the structure. This increases the conductivity of the material. The conductivity increases means the resistivity decreases. Thus when the temperature is increased in a semiconductor, the density of the charge carriers also increases and the resistivity decreases. For semiconductors it is said that they have a negative temperature co – efficient. So the value of temperature co –efficient of resistivity, α is negative.
*Variation of semiconductor*=
Silicon is a semiconductor. In semiconductors the forbidden gap between the conduction band and the valence band is small. At 0K, the valence band is completely filled and the conduction band may be empty. But when a small amount of energy is applied, the electrons easily moves to the conduction band. Silicon is an example for semiconductor. Under normal circumstances silicon act as a poor conductor. Each silicon atom is bonded to 4 other silicon atoms. The bonds between these atoms are co valent bonds where the electrons are in fixed positons. So at 0K, the electrons does not move within the lattice structure.
When the temperature in increased the forbidden gap between the two bands becomes very less and the electrons move from the valence band to the conduction band. Thus some electrons from the co valent bonds between the Si atoms are free to move within the structure. This increases the conductivity of the material. The conductivity increases means the resistivity decreases. Thus when the temperature is increased in a semiconductor, the density of the charge carriers also increases and the resistivity decreases. For semiconductors it is said that they have a negative temperature co – efficient. So the value of temperature co –efficient of resistivity, α is negative.
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