Thin, Radiation Tolerant AlGaAs Solid-State Photomuliplier Prototype Development

Silicon photomultipliers (SiPMs) are a compact, high-gain photodetector that can be used in nuclear instruments for capturing photons from large scintillator crystals for spectroscopy or thin films for imaging. One limiting factor for SiPMs is that the devices can degrade rapidly in highradiation environments. Using aluminum gallium arsenide (AlGaAs), a solid-state photomultiplier (SSPM) can be designed to address the radiation tolerance. GaAs has a larger absorption coefficient than silicon, and therefore, less material is required to provide an equivalent quantum efficiency. A thinner device provides less volume to become damaged by incident radiation. For Geiger-mode operation required for a SSPM, a high internal electric field is required. To provide this large field within a thin device, multiple tiered mesa designs have been studied. Radiation damage from neutrons show minimal impact on dark currents for the AlGaAs devices up to 10⁹ n / cm², while a noticable increase in silicon was measured. A prototype, triple mesa SSPMs have been produced for evaluation.