The influence of structural characteristics on the response of silicon avalanche photodiodes to proton irradiation

Different silicon avalanche photodiode structures are compared for the effects of 51-MeV protons on dark current, photocurrent, and noise. Large differences in depletion region volumes contributed to differences in sensitivity to bulk dark current increases. At high fluences, ionization damage appeared to be the dominant mechanism for dark current increases in some devices. Increases in 1/f-type noise and supplemental gamma ray testing indicate that these high dark current increases are due to surface damage effects. A discussion of structural parameters that may heighten radiation sensitivity is presented, including doping levels and p-n junction termination techniques.