With what considerations in view, a photodiode is fabricated ? State its working with the help of a suitable diagram

With what considerations in view, a photodiode is fabricated ? State its working with the help of a suitable diagram.
Even though the current in the forward bias is known to be more than in the reverse bias, yet the photodiode works in reverse bias, what is reason ?

It is fabricated with a transparent window to allow light to fall on diode.
When the photodiode is illuminated with photons of energy (hv > Eg) greater than the energy gap of the semiconductor, electron - holes pairs are generated. These gets separated due to the junction electric field (before they they recombine) which produced an emf.

Reason : It is easier to observe the change in the current, with change in light intensity, if a reverse bias is applied.
Alternatively,
The fractional change in the minority carrier current, obtained under reverse bias, is much more than the corresponding fraction change in majority 5 carrier current obtained under forward bias.