What happens when a p-n junction reaches its breakdown voltage?

When a p-n junction reaches its breakdown voltage, the device experiences a sudden, sharp increase in electric current.12

Under normal reverse-bias conditions, a p-n junction allows only a small leakage current to flow. However, once the reverse bias reaches the critical breakdown voltage, the junction's resistance effectively drops, allowing a significant current to pass through the material. This phenomenon is often driven by the avalanche effect, where high-energy electrons collide with atoms to release additional charge carriers, creating a cascading increase in conductivity.123

In most cases, this breakdown is a nondestructive event, provided that the resulting power dissipation is kept within safe limits. If the current is not properly controlled, the intense flow of electricity can lead to permanent damage, such as melting the semiconductor material. Because the breakdown voltage is dependent on factors like impurity concentration, it can be precisely engineered for use in components such as the Zener diode to regulate voltages in electronic circuits.123