Omnivision patent application US20150041627 "Partitioned silicon photomultiplier with delay equalization" by Eric A. G. Webster proposes 3-wafer stacked photomultiplying imager. The top wafer has photomultiplier diodes with quenchers, the bottom wafer has the readout electronics, while the mid interposer-wafer ensures equal-length interconnects to ensure the equal delay between the PDs in each pixel, and so improve the timing resolution:
