Proton Radiation Effects on HgCdTe Avalanche Photodiode Detectors

Space radiation damage and proton-induced transient effects were evaluated on 4.4-μm cutoff HgCdTe avalanche photodiode (APD) arrays developed by Leonardo DRS. Device performances as a function of total dose up to 100 krad (Si) were measured with ~60-MeV protons on three types of APD samples: 4 × 4 pixel APD fanout arrays with and without connection to a read-out integrated circuit (ROIC) and a 2 × 8 pixel photon-counting APD focal plane array (FPA). A gamma-ray test was also conducted to study ionization effects. Both APD arrays exhibited a small decrease in the quantum efficiency and a linear increase in the dark current with the proton fluence. The 2 × 8 pixel photon-counting FPA also exhibited an increase in the dark count rate with proton dose. After the proton irradiation and an overnight room-temperature warm-up, the APD dark currents at 80 K increased significantly in both types of APD arrays. All radiation damage to these HgCdTe APD arrays annealed out after baking them at >85 °C for several hours. Transient protons through the devices were found to cause large pulses at the detector output, but recover within 1 μs.