In n-type semi conductors the correct statement is/are(i) The fermi en...
In n-type semiconductors, the majority charge carriers are electrons, which are introduced by doping the semiconductor with impurities containing extra valence electrons (known as donor impurities). Let's analyze each statement given in the question to determine the correct options:
(i) The fermi energy level lies in between donor band and valence band:
The Fermi energy level represents the highest energy level occupied by electrons at absolute zero temperature (0 Kelvin). In n-type semiconductors, the Fermi energy level lies closer to the conduction band than the valence band. This is because the donor impurities introduce extra electrons into the conduction band, making it easier for electrons to move to higher energy states. Therefore, statement (i) is incorrect.
(ii) The fermi energy level lies in donor band and conduction band:
As mentioned above, the Fermi energy level lies closer to the conduction band in n-type semiconductors. It does not lie within the donor band, which represents the energy levels of the impurity atoms. Therefore, statement (ii) is incorrect.
(iii) The fermi energy increases with increasing temperature:
At absolute zero temperature, the Fermi energy level is at its lowest point. As the temperature increases, some electrons gain enough thermal energy to transition from the valence band to the conduction band. This causes the Fermi energy level to shift towards higher energies. Therefore, statement (iii) is correct.
(iv) The fermi energy decreases with increasing temperature:
Based on the explanation above, this statement contradicts statement (iii). Therefore, statement (iv) is incorrect.
From the above analysis, we can conclude that the correct options are (ii) and (iv), which are both incorrect statements.