What is recombination current? This term is used frequently to describe the mechanism of current flow in a forward biased PN junction. It is called "recombination current", where recombination is the process of conduction electrons filling holes in the valence band, thus eliminating an electron-hole pair. 
The issue with this terminology, is that elimination of an electron-hole pair seems to stop current, not cause or allow it. So to call a current "recombination current" makes it seem as though the current is made up of disappearing electrons and holes, a seeming contradiction. You could as well say that at rush hour on the highway, the traffic is made up of "parking traffic". 
So with this in mind, how is the phrase "recombination current" supposed to be interpreted? In effect, what is recombination current through a PN junction?
 A: The current in a forward biased pn-junction can be called recombination current because the current is finally due to recombination of electrons and holes inside the junction, either  in the depletion zone or in the neutral n- or p- regions. It is important to realize that this forward current is due to recombination of electrons and holes coming from different sides (n-doped and the p-doped) of the junction. Thus each electron-hole recombination event corresponds to the transport (and thus current) of one elementary charge across the pn-junction.   
A: Use Current = V/R, where the holes are moving. We don't think about electron movement for voltages, that's for physicists. Think about the positively directed current and the theory works. It's just confusing, because of all the charges and lack of good notation.
The recombination current is just the current across the junction. Outside the junction, there's no current until the depletion layer extends across the n-terminal. You just get the resistive p-block insulating flow. To get the total recombination current, you've got to add both the electron and the hole flow; but consider only one first. the generation is from heat, or light, and happens with a frequency.
A: The holes disappearing from the negative terminal cause the electrons from the battery to be used up. Which causes more electrons to be pushed from the negative terminal of the battery. similarly the electrons disappearing from the positive terminal cause electron in the p junction to be used up and delivered to the positive terminal of the battery.so if you consider a diode to be a black box, the electrons disappearing from the left are reappearing on the right (from the right to the left) and there is a net "FLOW" of charges hence the current. 
