The structure and properties of gallium arsenide photovoltaic cells were investigated using a wide range of analytical methods. Solar cells were exposed to intense gamma irradiation with a dose of 500 kGy. The radioactive isotope Cobalt-60 was used as the emitter. Fourier transform infrared spectroscopy (FTIR), ellipsometry, and spectrophotometry were used as optical measurement methods for observing the shift of permittivity, reflectance, and other surface investigation. Changes in thin-film composition were also analyzed by secondary-ion mass spectrometry (SIMS) by surface sputtering. Electrical characteristics were also observed. Minority carrier properties, junctions, or defects in semiconductor were investigated by scanning electron microscopy (SEM) with electron beam-induced current method (EBIC). Complementarily was proved diffusion of metals into thin layers of GaAs structure. This phenomenon affects the overall performance of the solar cell.