Avalanche Breakdown

Avalanche breakdown occurs in the opposite regime: LIGHTLY doped junctions, which have wide depletion layers. Here the electric field alone is not strong enough to rupture bonds directly the way it is in Zener breakdown. Instead, the thermally generated minority carriers already present are accelerated by the field as they cross the wide depletion region, gaining enough kinetic energy to COLLIDE with lattice atoms and break covalent bonds on impact, generating new electron-hole pairs. These newly created carriers are themselves accelerated and collide again, producing yet more carriers -- a cumulative, self-multiplying chain reaction (an 'avalanche') of charge carriers sweeping across the junction, which sharply reduces the reverse resistance and causes the diode current to rise sharply, exactly as in Zen …