The effect of neutron irradiation on silicon photodiodes

Abstract

Neutron radiation testing was performed on a total of 125 silicon photodiodes to investigate the changes in the device parameters after neutron exposure. Californium-252 source was used to irradiate these photodiodes with 1 MEV equivalent neutrons having fluences in the range of 5x1Ol1 to lOI4 N/cm2. The photodiode forward voltage drop, ideality factor and series resistance were found to increase after neutron exposure. The increased series resistance was found to cause a degradation in diode photocurrent linearity. An empirical expression for post neutron changes in photodiode linearity is presented. Neutron induced changes in the photodiode shunt resistance and dark current have been modeled using simple expressions. These expressions allow device designers to estimate changes in photocurrent linearity, shunt resistance and dark current after neutron exposure. No post neutron change in the UV quantum efficiency of diodes without rkcombination in the front region was observed. This suggests that neutron irradiation does not affect the Si-Si02 interface recombination velocity of p-n junction diodes. INTRODUCTIO N

Time resolved radiated power during tokamak disruptions and spectral averaging of AXUV photodiode response in DIII-D

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