International Radiation Detectors, Inc.

Radiation Hardness

The second unique property of the UVG diodes is their radiation hard, junction passivating, oxynitride protective entrance window.This super-hard window makes them extremely stable after exposure to intense flux of UV photons. They show less than 2% responsivity degradation after megajoules/cm² of 254 nm and tens of kilojoules/cm2 of 193 nm photon exposure. Because of the oxynitride window, UVG photodiodes did not show any change in uv-visible quantum efficiency after their exposure to 100% relative humidity for several weeks. This unique feature enables their use without the commonly used fused silica protective window. This open face configuration is extremely advantageous in applications where the fused silica window interference effects are problematic.

Owing to these outstanding properties, national laboratories like NIST and PTB (Germany) are evaluating UVG photodiodes for use as transfer standards.

As n-on-p diodes are more radiation-hard than the more common p-on-n devices [1], UVG diodes are better suited for space missions than conventional silicon photodiodes. UVG photodiodes with 4 mm and 5 mm diameter active area are being used in the Multi-Angle Imaging Spectro Radiometer (MISR) launched in December 1999as part of NASA's Earth observing system [2]. These devices will also be used aboard an Argentinean satellite.

References

R. Korde et. al. "The effect of Neutron Irradiation on Silicon Photodiodes" IEEE Trans. on Nuclear Sciences, Vol. 36, 2169-2175 (1989).

C. Jorquera et. al. "Design of New Photodiode Standards for use in the MISR In-Flight Calibrator" Proc. of IGARSS' 94, IEEE Catalog Number 94CH3378-7, 1998-2000 (1994).