A screened Coulomb scattering module for displacement damage computations in Geant4

A new software module adding screened Coulomb scattering to the Monte Carlo radiation simulation code Geant4 has been applied to compute the nonionizing component of energy deposited in semiconductor materials by energetic protons and other forms of radiation. This method makes it possible to create three-dimensional maps of nonionizing energy deposition from all radiation sources in structures with complex compositions and geometries. Essential aspects of previous NIEL computations are confirmed, and issues are addressed both about the generality of NIEL and the ability of beam experiments to simulate the space environment with high fidelity, particularly for light ion irradiation at very high energy. A comparison of the displacement energy deposited by electromagnetic and hadronic interactions of a proton beam with published data on GaAs LED degradation supports the conclusion of previous authors that swift light ions and slower heavy ions produce electrically active defects with differing efficiencies. These results emphasize that, for devices with extremely small dimensions, it is increasingly difficult to predict the response of components in space without the assistance of computational modeling. Index Terms--Computational physics, displacement damage, GaAs, Geant4, Monte Carlo, NIEL, nonionizing energy loss, nuclear stopping.