What is quantum mechanical tunneling in zener?

Quantum mechanical tunneling in Zener diodes refers to the phenomenon where charge carriers, such as electrons, can pass through a potential energy barrier even when they do not possess enough energy to overcome it classically. In Zener diodes, this occurs when a reverse bias is applied, causing a strong electric field that enables electrons to tunnel from the valence band to the conduction band, resulting in a controlled breakdown at a specific reverse voltage. This process allows Zener diodes to maintain a stable output voltage, making them useful for voltage regulation in electronic circuits.