International Radiation Detectors, Inc.

Polarization Sensitivity

The responsivity of silicon photodiodes can be affected by the degree of polarization and the azimuth of incident radiation. When a detector is used obliquely to incident radiation, polarization effects arise. The oxide thickness of the photodiode will affect the polarization sensitivity by means of surface reflectivity and absorption.

Polarization dependence of the diode responsivity has been reported in 50 nm to 150 nm spectral range. This short wavelength polarization dependence implies that absorption in the oxide layer is the dominant loss mechanism (since there is little reflection loss) and it has been shown that absorption increases with larger angle of incidence due to increased path length.. As oxide thickness is decreased, this polarization effect is reduced and at an oxide thickness of 8 nm (AXUV series diodes), this effect is negligible.

The AXUV photodiodes have been successfully used recently to measure polarization of the EUV sources. A Mo/Si multilayer interference coating was deposited directly on the AXUV100 photodiode surface to selectively transmit the p-polarized component of 13.5 nm and to reflect the s-polarized incident radiation.

Polarization sensitivity of the SXUV diode responsivity between 130 and 600 nm is described in the literature.