Si(Li) detectors with thin dead layers for low energy X-ray detection

Regions of incomplete charge collection, or dead layers, are compared for Si(Li) detectors fabricated with Au and Pd entrance-window electrodes. The dead layers were measured by characterizing the detector spectral response to X-ray energies above and below the Si Kα absorption edge. It was found that Si(Li) detectors with Pd electrodes exhibit consistently thinner effective Si dead layers than those with Au electrodes. It is demonstrated that the minimum thickness required for low-resistivity Pd electrodes is thinner than that required for low-resistivity Au electrodes, which further reduces the signal attenuation in Pd/Si(Li) detectors. A model based on Pd compensation of oxygen vacancies in the SiO₂ at the entrance-window Si(Li) surface is proposed to explain the observed differences in detector dead-layer thickness