I can understand that in the depletion region of a diode more covalent bonds are broken(more electrons goes to conduction band) with more temperature hence we say that the reverse saturation current is dependent upon the temperature i.e. thermal energy added.
But what is the argument which explains why the reverse saturation current is independent from the reverse voltage(at least until the zener breakdown)? (Until zener breakdown why does the increasing reverse voltage have no effect on the reverse current?)
But at some "zener" point something happens and the electrons starts to avalanche and create more electrons. But why doesnt this thing happen gradually? I mean the reverse saturation current is constant untill the avalanche why? Things start to happen at a particular point all of a sudden not gradually.