The Effects of High Energy Protons on Shielded Space Solar Cells

We discuss the applicability of the displacement damage dose method and the non-ionizing energy loss (NIEL) concept to the effect of protons on GaAs devices. Comparison of the relative damage coefficients (RDCs) for different GaAs devices with the energy dependence of the proton NIEL shows differences for proton energies > 10 MeV. However, since actual RDCs are always bound between the total and Coulombic NIELs, calculations were performed for the total displacement damage dose using both NIEL curves to determine the range of dose expected for devices shielded with various thickness of fused silica coverglass. These calculations were performed for two different incident proton spectra. The overall effect of using the total or Coulombic NIEL for calculating the total displacement dose deposited is minimal until extreme thicknesses of shielding are used.