Spatial resolution and nature of defects produced by low-energy proton irradiation of GaAs solar cells

Abstract

AlGaAs/GaAs solar cells with ∼0.5-μm-thick Al0.85Ga0.15As window layers were irradiated using isotropic and normal incidence protons having energies between 50 and 500 keV with fluences up to 1×1012 protons/cm2. Although the projected range for these protons varies from 0 to more than 4.5 μm, the recombination losses due to the irradiation-induced defects were observed to be maximum in the vicinity of the AlGaAs/GaAs interface and the space-charge region irrespective of the proton energy. This was found by analyzing spectral response measurements. The results are explained by using a model in which the interaction of as-grown dislocations with irradiation-induced point defects is considered.