US Patent 10515993 Stacked photodetector assemblies

An exemplary stacked photodetector assembly includes a first wafer and a second wafer bonded to the first wafer. The first wafer includes a SPAD and has a thickness T1 configured to minimize absorption by the first wafer of photons included in light incident upon the first wafer while the SPAD is in a disarmed state. The second wafer has a thickness T2 configured to provide structural support for the first wafer. The stacked photodetector assembly includes a fast gating circuit electrically coupled to the SPAD and configured to arm and disarm the SPAD.