Question

The main cause of avalanche breakdown is

• A. ionisation by collision.
• B. high doping.
• C. recombination of electrons and holes.
• D. low doping.

Answer 1

The correct option is A ionisation by collision.

Avalanche breakdown is caused by impact ionization of electron-hole pairs. A very little current flows under reverse bias conditions and depletion region increases. The electric field in the depletion region of a diode can be very high. Electron/holes that enter the depletion region undergo a tremendous acceleration. As these accelerated carriers collide with the atoms, they can knock electrons from their bonds, creating additional electron/hole pairs and thus additional current. As these secondary carriers are swept into the depletion region, they too are accelerated and the process repeats itself.