The Laser 2000 range of biased photodetectors delivers much higher bandwidths and higher responsivities than may be achieved with bare un-biased detectors.
This is achieved as the reverse bias creates a strong electric field in the p-n junction which increases the drift velocity of the carriers, reducing their transit time. At the same time, the reverse bias also increases the width of the depletion layer, thereby reducing junction capacitance and improving the response time.
Furthermore, the increased width of the depletion layer leads to a larger photosensitive area, which makes it much easier to collect more light.