Theoretical and Experimental Determinations of Neutron Energy Deposition in Silicon

Abstract

Theoretical calculations have been made of the energy deposited in silicon in ionization and elastic interactions by neutrons in the energy range of 60 keV to 15 MeV. In contrast to earlier determinations, care was taken to calculate accurately the effects of atomic recoils. These are of primary importance for permanent effects in silicon at all neutron energies and account for about 30% of the transient ionization at 14 MeV. To test the calculation of the energy deposited by 14 MeV neutrons, experiments were performed with a pulsed d-t generator. The experimental values in rads per unit fluence were (11 ± 2) × 10-10 rad-cm2 for special p-n junctions and (8 ± 2) × 10-10 rad-cm2 for power transistors. Both experimental values agree, withi jerror, with the calculated value of (8 ± 1) × 10-10 rad-cm2. The calculated variation of radiation damage in silicon with neutron energy was compared with existing experimental data. There is general agreement of theory with experiment from 200 keV to 14 MeV.