Effects of proton irradiation on a SAPHIRA HgCdTe avalanche photodiode array

We present the results from a radiation damage test of a HgCdTe avalanche photodiode (APD) array developed by Leonardo UK for potential NASA space lidar applications. The device being tested is a high-speed variant of the SAPHIRA family HgCdTe APD arrays used in astronomy. Test results show that the device remains fully operational at normal bias level under proton flux anticipated in space. The average dark current started to rise above the noise floor after 2 krad(Si) accumulated dose. However, the APD dark currents increased by more than an order of magnitude after the device was warmed up to room temperature for two hours and cooled to 80 K again. The dark currents returned to their pre-irradiation levels after being heated to 344 K (70°C) for about two hours. There was little change in the quantum efficiency and APD gain after 50 krad(Si) and annealing.