semiconductor physics

[rgshankar76]

why is that the fermi level should be constant throught the system under equilibrium conditions? can I know the physical outcome of that condition or the violation of the same?

[ZapperZ]

why is that the fermi level should be constant throught the system under equilibrium conditions? can I know the physical outcome of that condition or the violation of the same?

Because the Fermi level (and NOT to be confused with the chemical potential, especially in a semiconductor) is the highest energy of each component of the system, and THIS is the level that is in contact with other components, the surrounding, etc. Therefore, at thermodynamic equilibrium, via the Thermo's Zeroth Law, all the Fermi level are at the identical "reference" level.

Zz.