Formation of Depletion Region?

[Roopa]

How the depletion region is formed? It is formed because of the recombination(due to diffusion) on either sides of p-n junctions. So, then the recombinated Boron and phosphorous come to the close to depletion region. If the depletion region is formed of recombination there will be immobile charges in depletion region. It means they don't have any charge. If they don't have charge, how they are acting as capacitors? and how the electric field produced in the depletion region?
Please help me I am very much confused about these........

 

[bountyhunter]

Analogy: The depletion region itself is the "space" between the capacitor plates which are formed by the doped region (with mobile charge carriers in them)..

That's why a PN junction needs a small voltage potential like 0.6V to make the E field strong enough to get charge carriers to cross the depletion region.

 

[BrownOut]

If the depletion region is formed of recombination there will be immobile charges in depletion region. It means they don't have any charge.

Why would you say immobile charges don't have any charge??? The are charges, immobile or not. In fact, what is in the depletion region are charged molecules (aka ions), fixed into the crystal lattice. The have a net charge, positive for the N-side and negative for the P-side.