Junction breakdown occurs:

Junction breakdown occurs: Correct Answer under reverse bias

There are generally two mechanisms of junction breakdown Avalanche breakdown and Zener

breakdown both of which occur in reverse bias of the junction:

Zener breakdown:

• When we increase the reverse voltage across the p-n junction diode, the electric field across the diode junction increases
• This results in a force of attraction on the negatively charged electrons at the junction
• This force frees electrons from its covalent bond and moves those free electrons to the conduction band

Avalanche Breakdown:

• Electron-hole pairs thermally generated in the depletion region are accelerated by the external reverse bias
• Electrons are accelerated towards the n side and holes towards the p side
• These electrons can interact with other Si atoms and if they have enough energy can knock off electrons from these Si atoms
• This process is called impact ionization and leads to the production of many electrons
• This causes the rapid rise in current