JEE Main & Advanced Physics Semiconducting Devices Reverse Breakdown

If the reverse biased voltage is too high, then breakdown of P-N junction diode occurs. It is of following two types

(1) Zener breakdown : When reverse bias is increased the electric field across the junction also increases. At some stage the electric field becomes so high that it breaks the covalent bonds creating electron, hole pairs. Thus a large number of carriers are generated. This causes a large current to flow. This mechanism is known as Zener breakdown.

(2) Avalanche breakdown : At high reverse voltage, due to high electric field, the minority charge carriers, while crossing the junction acquires very high velocities. These by collision breaks down the covalent bonds, generating more carriers. A chain reaction is established, giving rise to high current. This mechanism is called avalanche breakdown.