Please explain negative bias and "a stronger field to sweep carriers out of depletion"
what changes to the circuit schematic does this imply,4

You'd connect the anode of the photodiode to a negative voltage instead of to ground.

what does &quot;... providing a stronger field to sweep carriers out of the depletion ...&quot; mean?

It means that with a stronger reverse bias, the field in the depletion region of the diode will be stronger, and therefore optically excited carriers (electrons and holes) will be swept out of the junction more quickly, increasing the bandwidth of the detector.