Which of the following occurs in PN junction diodes when the electric field in the depletion layer increases to the point where it can break covalent bonds and generate electron hole pairs?

Correct option is C

Zener breakdown is a phenomenon that occurs when a pn junction is reverse-biased and electrons tunnel from the valence band of the p-type region to the conduction band of the n-type region. This causes a sudden increase in reverse current.