Radiation hardness studies of InGaAs and Si photodiodes at 30, 52, & 98 MeV and fluences to 5x10^11 protons/cm^2
Here we report the results of an investigation into the effects of ionizing radiation on commercial-off-the-shelf InGaAs and Si photodiodes. The photodiodes were exposed to 30, 52, and 98 MeV protons with fluences ranging from 10^8 - 5x10^11 protons/cm^2 at the Indiana University Cyclotron Facility. We tested the photodiodes for changes to their dark current and their relative responsivity as a function of wavelength. The Si photodiodes showed increasing damage to their responsivity with increasing fluence; the InGaAs photodiodes showed significantly increased dark current as the fluence increased. In addition, we monitored the absolute responsivity of the InGaAs photodiodes over their entire bandpass. Our measurements showed no evidence for broadband degradation or graying of the response at the fluences tested. All measurements in this investigation were made relative to detectors traceable to NIST standards.