Proton-Neutron Damage Correlation in Semiconductors

Abstract

The results of a study program to determine a proton-neutron damage correlation in semiconductors are presented. Three approaches were undertaken: Theoretical, Empirical using data from existing literature, and Experimental. The results of the theoretical studies show that damage processes between the neutrons and protons are basically different in silicon. Damage from neutron irradiation is characterized by the effective cross sectional area of the cluster of displaced atoms and is relatively independent of the type of impurity. Damage from protons, on the other hand, is dominated by the defects involving impurities. For this reason, theoretically derived damage "cross sections" for each different type of bambarding particle must be based on different (and independent) physical properties of the semiconductor material. In the empirical study using the data from the literature, it was not possible to determine a reliable proton-neutron correlation. Spread in neutron damage data due to irradiation of different types of devices, inadequate data reporting and no data on similar type semiconductors under both neutron and proton irradiation contributed to this result. The experimental program was carried out on silicon solar cells under fission and moderated neutrons and proton energies of 48.5, 68.9, and 96.5 Mev. A proton-neutron correlation for the diffusion length damage was determined and the ratios of the proton to neutron damage varied frmn 0.6 to 4.8 depending on the proton energy and neutron spectrum.