Well Zener diodes operate as a voltage regulator because of the Zener effect-Quantum tunneling . Quantum tunneling is the effect when an electron faces an energy barrier but after the energy barrier there is a energy downhill and it has a propability of "passing through " the energy hill.
But as far as I can understand the energy barrier in a zener diode is bigger than the energy downhill so the electron must be excited to even have the propability of passing through the energy hill . Do only excited electrons can move through the energy hill and become mobile charge carriers?
What am I missing?