The effects of low-energy proton irradiation on partially shielded GaAs solar cells

The effects of low-energy proton radiation incident on a small strip at the edge of GaAs space power solar cells has been measured. Three separate parameters have been studied; the proton energy, total proton fluence, and the fraction of the strip irradiated. Finally, the response of cells irradiated with a spectrum of protons representative of the geosynchronous space environment has also been measured. The proton irradiation, whether mono-energetic or a spectrum, initially degrades the cells. As irradiation continues, the degradation slows, ceases and reverses. At high doses, nearly all of the induced degradation is removed and the cell becomes impervious to further irradiation. The variation of power loss versus fraction of the strip region exposed is nonlinear, with 60% of the total degradation occurring after exposing only 25% of the edge. The effects may be minimized by either pre-irradiation of the strip region or partial shielding. Protection may not be required for some radiation environments or missions