Explanation
Ga has valency of 3.
Absence of one electron creates the positive charge of magnitude equal to that of electronic charge.
Impurity increases the conductivity.
Resistance of conductors (Cu) decrease with decrease in temperature while that of semiconductors (Ge) increase with decrease in temperature.
In insulators, the forbidden energy gap is largest and it is of the order of 6eV.
Among the given materials copper is the best conductor of electricity.
In superconductors, the current flows on the surface so that it exactly cancels the magnetic field inside the metal.
Therefore statement (b) is not correct.
Boron is trivalent.
In P-type semiconductors, holes are majority charge carriers and electrons are minority charge carriers.
Antimony is a fifth group impurity and is therefore a donor of electrons.
Antimony is pentavalent
In sample x no impurity level seen, so it is undoped. In sample y impurity energy level lies below the conduction bond so it is doped with fifth group impurity.
In sample z, impurity energy level lies above the valence band so it is doped with third group impurity.
The temperature co-efficient of resistance of a semiconductor is always negative.
The resistance of semiconductor decreases with the increase in temperature.
At absolute zero temperature semiconductor behaves as insulator.
Formation of energy bands in solids are due to Pauli’s exclusion principle.
In P-type semiconductors, holes are majority charge carriers.
Conductivity of semiconductors increases with rise in temperature.
In N–type semiconductors, electrons are majority charge carriers.
When a strong current passes through the semiconductor it heats up the crystal and covalent bonds are broken. Hence because of excess number of free electrons it behaves like a conductor.
In semiconductor, the forbidden energy gap between the valence band and conduction band is very small, almost equal to kT. Moreover, valence band is completely filled where as conduction band is empty.
Also know that in an N-type semiconductor the donor energy level lies just below the conduction band.
In N-type semiconductor impurity energy level lies just below the conduction band.
In conductors valence hand and conduction hand overlaps.
Because as its pentavalent impurity
One atom of pentavalent impurity, donates one electron.
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