Junction diode - unequally doped sides

[hitcool007]

Why does the depletion layer penetrate a lightly doped side of a p-n junction diode?? Consider that there is a lightly doped p-side and a heavily doped n-side in a p-n junction diode , which is connected to a dc power supply in reversed biased. Now, I've read that depletion layer penetrates the p-side in this case. But i could not figure out the reason behind it. So, Can u please explain me the mechanism involved in terms of the movement of electrons in the circuit.
Im in a faulty assumption that the side in which the diode is more heavily doped is bound to be penetrated more by the depletion layer..
(-I've completed my intermediate)

 

[mfb]

The sum of electrons and holes stays constant (the whole thing does not get a significant net charge). If the hole density is larger, the volume with holes is smaller, and vice versa.

 

[hitcool007]

ok,, but i dint get the answer to my question!

 

[mfb]

In this case, I don't understand the question. You have depletion at both sides as electrons from one side move into the holes at the other side, unless your diode is in a conducting mode.