Displacement damage induced by cosmic rays in silicon devices using geant4 toolkit for space applications

In the space environment the dominant radiation at energies above 50 MeV/nucleon is constituted by the Galactic Cosmic Rays (GCRs) which are capable to inflict permanent damage to silicon devices. In particular the displacement damage was analyzed and the Non-Ionizing Energy Loss (NIEL) was calculated both at high and low energies in order to estimate the displacement damage for the entire energy range of the space radiation environment. Of particular relevance was the development of an improved implementation of the Geant4 single scattering model. This modification gives the possibility to calculate the Coulomb scattering contribution to the NIEL for heavy nuclei at high energies. Moreover the GCR fluxes of the ISO model 15390 was introduced in Geant4 as a particle generator in order to reproduce the solar modulation effect on GCRs. For instance, using the ISO model of GCRs fluxes and the NIEL for all the nuclei, we estimated the expected NIEL-Dose absorbed by a silicon sample during one year mission. In addition Hall effect measurements were performed in our laboratory on silicon samples of different resistivities which are usually used as substrates for the fabrication of devices employed in space missions