Charge supply by a Reverse-biased PN Junction

In the following applet, use the scroll bar to set a negative bias voltage (reverse bias), say - 0.4 Volts. Now, again you are inside the p-type region (red color rectangle in the upper diagram). Look at the junction and see what carriers are moving into p-side. [If it is not clear whether the electrons and holes are moving in or out, change the voltage a bit.]

Once again, do not worry about the carriers moving out from the region.

Into the p-side, holes move in by the reverse-biased pn junction. These holes originate from the minority carrier holes in the n-side. The number is very small.

Example: In the n-side, n = Nd = 1E16 cm-3. p = ni2/n = 1E20 / 1E16 = 10,000 cm-3. There are only 10 thousand holes per cm3 while there are 10 thousand trillion electrons per cm3.

Conclusion: The reverse-biased pn junction supplies a very small amount of majority carriers. These are thermally generated carriers in the other side of junction.