About the scatter of displacement damage and its consequence on the NIEL scaling approach

The Non Ionizing Energy Loss (NIEL) is the metric conventionally used to scale displacement damage degradation mechanisms. The degradation of many electrical parameters are scaled according to the NIEL. But along the years, some deviations were observed between the experimentally measured damage factors and the NIEL. This has been especially observed for high energy protons (>30 MeV in GaAs), for which measurements have been demonstrated to follow the “Coulombian” part of the NIEL preferably than the total NIEL. Up to now no clear understanding of this mechanism has been given. This paper proposes to interpret these discrepancies as a statistical bias induced by the nature of the deposition of the displacement damage dose. The reliability of the NIEL is discussed as a function of the deposited fluence.