Degradation characterization of induced junction photodiodes under ultraviolet irradiation

Induced junction photodiodes have shown great stability and predictability at visible wavelengths, but they may undergo responsivity changes when exposed to ultraviolet (UV) irradiation. When using induced junction photodiodes in a predictable quantum efficient detector (PQED) with operation range extended to UV, the irradiation hardness of photodiodes is of critical concern. In this study, two different types of induced junction photodiodes, with either oxide or nitride passivation layers, were exposed to UV irradiation at 300 nm, 280 nm, 254 nm and 222 nm wavelengths. Their photocurrent was monitored during the irradiation and their UV and visible range spectral responsivities were compared before and after the irradiation. Our results show excellent stability for the nitride coated photodiodes when irradiated at 300 nm, but clear degradation when irradiated at 280 nm, whereas the oxide coated photodiodes remained stable after irradiation at 280 nm and 254 nm, and degraded only at 222 nm. This significant novel outcome opens the way to extend the predictability of PQED to the previously inaccessible wavelength range from 250 nm
to 450 nm.