Degradation of particle detectors based on a-Si:H by 1.5 Mev He 4 and 1 MeV protons

Abstract

Photoconductivity as a measure of the majority carrier mobility–lifetime product is monitored in intrinsic amorphous silicon film (a-Si:H) when subjected to a 1.5 MeV He 4 beam. In a second step we looked at the changes of device performance in a 5 μm thick a-Si:H based detector structure which was subjected to a 1 MeV proton beam that assures a homogeneous damage profile. We find that the Rose coefficient increases to near unity after strong irradiation indicating the transition from bi- to monomolecular recombination. The p–i–n device shows changes that can be related to the properties of the thick intrinsic layer. As a by-product we can reconstruct the particle beam profile using the analytical fit to the fluence dependence of photosensitivity.