Design of a compact, radiation tolerant AlGaAs Geiger photodiode

The Geiger photodiodes, or single photon avalanche photodiodes, for a radiation tolerant solid-state photomultiplier (SSPM) are being designed using Aluminum Gallium Arsenide (AlGaAs) and are less than 1 mu m thick. Studies on the changes in dark current compared to silicon from thermal neutron damage were conducted demonstrating that the design concept is feasible, as the device sensitivity to incident radiation is low relative to silicon devices. To achieve the required high fields for Geiger mode operation within a thin device, a triple mesa structure was developed, and simulations show a favorable field profile that constrains the highest electric fields to the middle of the device and keeps the field strength at all corners and surfaces 3-6x lower than the field in the center at breakdown.