Abstract
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An n-SOI microdosimeter which has been proposed
as a device for predicting the occurrence of single event effects
in semiconductor electronics in the high-energy, mixed heavy ion
space radiation environment has been investigated to better understand
the charge collection geometry and charge collection mechanisms.
Ion beam induced charge collection studies using 20 MeV
C ions, 5.5 MeV He ions, and 2 MeV H ions were carried out,
and the effects of different bias conditions, angles of ion incidence,
and coincidence analysis were observed to understand the sensitive
volume geometry. The energy response of the n-SOI microdosimeter
has been observed to exhibit an over-response of 56%,
113%, and 23% for the above ions compared to expected energy
depositions calculated using SRIM 2008. No relationship between
particle LET AU: Please provide spelling for “LET” and the enhance
energy response was apparent. A comparison of experimentally
measured and simulated spectra suggest a cylindrical charge
collection geometry despite the physical rectangular parallelepiped
geometry of the p-i-n diode. This was supported by observing the
response of the microdosimeter to ions at oblique ion incidence.
A simplified model of diffusion charge collection found that diffusion
charge collection contributes to the low-energy tail observed
in experimental spectra, but does not account for the observed enhanced
energy response. This supports the current theory that the
enhanced energy response is a result of a displacement current produced
when charge carriers in the substrate induce charge in the
SOI layer due to the parasitic capacitance of the buried SiO insulating
layer.