Characteristics of CMOS avalanche photodiodes at cryogenic temperatures

To replace PMTs for readout of optical photons from scintillation materials in harsh environments, prototype solid-state photodetectors has been developed to operate in harsh environments, which implies temperatures down to 4°K and magnetic fields up to 7 T. A photodiode structure developed out of RMD´s CMOS SSPM technology shows avalanche multiplication at temperatures down to 4°K when operated in a proportional mode (below breakdown). The diode and photodetector characteristics are discussed, providing information on the implementation of these devices for the HIFROST target, which will be used to study the proton spin polarizabilities. The photodetector shows a quantum efficiency of ~45% at 532 nm for 4°K operation with a dark current of ~0.1 ¿A/mm² and a gain of ~100 for an operating bias of 31.8 V. Light pulses of 500 photons were easily read out using amplifiers operated at room temperature.