semiconductor physics question about break down voltage...

[AznMaverick]

what causes the current at the break down voltage to be so high in zener diodes?

 

[f95toli]

Zener breakdown only occurs in highly doped PN-diodes.
In Zener diodes the conduction and valance band on opposite sides of the junction are so close together that electrons may tunnel from the valence band on the p-side into the conduction band on the n-side, this process will start as soon as the reverse-bias is higher than some threshold value.