Effects of Radiation Damage on the Behavior of GaAs p-n Junctions

This work illustrates the use of radiation damage as a "tool" enabling one to learn more about the conduction and injection mechanisms operative in GaAs p-n junctions. This is done by varying the minority carrier lifetimes by means of radiation damage and noting the resulting changes in various measured parameters. The electroluminescence (E.L.) and current in "lightly" doped diodes (~2 × 1017 donors/cm3) and their behavior after 2-MeV electron irradiation indicate that, although most of the recombination occurs within the depletion region, those few electrons that do succeed in being injected into the conduction band of the p-type side are the ones responsible for the E.L. In the case of "heavily" doped diodes (~2 × 1018 donors/cm3) at nitrogen temperature the E.L. occurs within the depletion region and is described by the "band-filling" model. The "band-filling" model also describes the behavior of the increase in current resulting from radiation damage. Short circuit current measurements during irradiation indicate that the diffusion length of electrons is much greater than the diffusion length of holes in diffused junctions, and gives additional information about the rate of defect introduction.