This type of break down occurs when a high reverse voltage is applied to a lightly doped junction diode as shown. In this case , the minority electron of the p side acquire high kinetic energy with which they knock out the valence electrons of the host atoms producing electron-hole pairs. These electron hole pairs gain kinetic energy from the electric field and in turn produce more and more electron pairs. This is called avalanche multiplication which occurs in a very short time to give large reverse current.