Displacement Damage and Dose Enhancement in Gallium Arsenide and Silicon

Calculations were made of dose and displacement damage rate profiles in GaAs and Si for electron beams and gamma rays. Electron flux energy spectra as a function of position were calculated using the ONETRAN code. Displacement cross-sections were calculated by integrating the Mott cross section using threshold energies of 10 eV for GaAs and 12.9 eV for Si. Profiles were calculated for the electron beam energies of 0.6 and 1.2 MeV. The displacement rate profiles vary with material and beam energy as determined by the changes of the electron energy spectrum and the different shapes of the GaAs and Si displacement cross sections. Displacement rate and dose profiles were also studied for both directions of the gamma rays normal to a Au/GaAs and Au/Si interface. An enhancement of the displacement damage rate at the Au/GaAs interface is observed when the gamma rays are incident from the gold side. This enhancement is not seen in the corresponding Au/Si case. With the gamma rays incident from the GaAs or Si side, the displacement damage rate profile is found to be proportional to the dose profile.