Radiation tests of single photon avalanche diode for space applications

Single photon avalanche diodes (SPADs) have been recently studied as photodetectors for applications in space missions. In this presentation we report the results of radiation hardness test on large area SPAD (actual results refer to SPADs having 500 μm diameter). Dark counts rate as low as few kHz at −10 °C has been obtained for the 500 μm devices, before irradiation. We performed bulk damage and total dose radiation tests with protons and gamma-rays in order to evaluate their radiation hardness properties and their suitability for application in a Low Earth Orbit (LEO) space mission. With this aim SPAD devices have been irradiated using up to 20 krad total dose with gamma-rays and 5 krad with protons. The test performed show that large area SPADs are very sensitive to proton doses as low as 2×108 (1 MeV eq) n/cm2 with a significant increase in dark counts rate (DCR) as well as in the manifestation of the “random telegraph signal” effect. Annealing studies at room temperature (RT) and at 80 °C have been carried out, showing a high decrease of DCR after 24–48 h at RT. Lower protons doses in the range 1–10×107 (1 MeV eq) n/cm2 result in a lower increase of DCR suggesting that the large-area SPADs tested in this study are well suitable for application in low-inclination LEO, particularly useful for gamma-ray astrophysics.