Low-energy proton bombardment of GaAs and Si solar cells

GaAs, Si n/p, and Si p/n solar cells were irradiated with 185-530 keV protons. The short-circuit current of the GaAs and the open-circuit voltage of the Si cells decreased severely as a result of bombardment. The short-circuit current of the Si cells was independent of flux at first, but it then fell rapidly. The damage produced in both the GaAs and Si cells increased with the proton energy. A model which accounts for the proton range satisfactorily explains the experimental results. This model predicts that the maximum damage rate in short-circuit current will occur at proton energies of 4-6 MeV for cells irradiated at 45° with respect to the beam. Above this energy, Rutherford-type behavior is expected.