Re: Diode breakdown
this is taken from a web page..this might answer ur qn clearly
when the diode was reverse-biased (p-region negative with respect to the n-region) that the only current which flows is the reverse saturation current, resulting from the few thermally generated minority carriers which can fall down (or up) the barrier.If we make the reverse bias even greater, the same current flows, but the carriers pick up more energy as they fall down the (now larger) junction potential. As they do this, it is possible for them to pick up so much energy, that when they collide with a lattice site, they create an additional electron-hole pair through a process called impact ionization.When this occurs, we now have current consisting of two electrons and one hole. These additional carriers can themselves collide and generate additional electron hole pairs as well. The current now consists of five electrons and two holes. This process is called avalanche multiplication.because we start with one carrier, and through a succession of impacts create more and more current. This process can in fact run away, much like an avalanche on a snowy mountain side, in a process called avalanche breakdown.