In intrinsic semiconductor, i have learned that fermi level is weakly dependent on temperature and it is sited between Ec and Ev.
In this case, I have some questions.
What could happen to fermi level if I increase the temperature,
Does fermi level decrease to the level that is lower than Ev…?
Then can this semiconductor act like conductor?
I know this question must be weird
Best Answer
While the Fermi level is dependent on the temperature, most easily seem through the relation to effective band density of states, something else more drastic will happen if you raise the temp. Regardless of what your doping levels might be, the number of intrinsic carrier pairs will start increasing. As the number of intrinsic carriers surpass the doping carrier concentrations, the Fermi level will be pulled back to midgap. What you can do, however, is dope beyond a bands effective density of states, I.e. degenerate doping. Then your Fermi level will rise above the conduction band, or drop below the valence band. And yup, these sort of heavily doped semiconductors behave somewhat like poor metals. Other neat things like Esaki diodes can use this principle.