Photodiode current equation

Question

The current in photo diode because of generation rate G and depletion width W is given as qGW (neglecting diffusion currents).

When the light is incident on the diode excess carriers are generated in depletion region in pairs and these are swept to respective P and N regions.

If the above is true, then why we are not taking current because of both holes and electrons i.e. current should be 2qGW.

Answer 1

We agree that current is constant in a circuit.

Take an arbitrary point in your voltage source - diode circuit. Make a cut. How many charges per second flow through that? That's current.

You'll see that for every recombination, exactly one electron (or one hole) flows. I don't see how that would lead to a factor of 2.