US Patent 11587960 Photodetector

A photodetector device comprising n-type and p-type light absorbing regions arranged to form a pn-junction and n+ and p+ contact regions connected to respective contacts. The light absorbing regions and the contact regions are arranged in a sequence n+ p n p+ so that, after a voltage applied between the n+ and p+ contacts is switched from a reverse bias to a forward bias, electrons and holes which are generated in the light absorbing regions in response to photon absorption drift towards the p+ and n+ contact regions respectively, which causes current to start to flow between the contacts after a time delay which is inversely proportional to the incident light intensity.