16%-efficient GaAs solar cell after 10/sup 15/ cm/sup -2/, 1 MeV radiation

Efficiency and related device parameter data are presented for p-n GaAs solar cells before and after irradiation with 1 MeV electrons for a total fluence of 10/sup 15/ cm/sup -2/. The post-radiation efficiency of most cells dropped to 75% of the pre-irradiation value. In separate experiments, the effects of base doping and emitter thickness were investigated. A base doping around 1*10/sup 17/ cm/sup -3/ gave the highest 1 sun, AM0 efficiencies both before and after irradiation at 22.0% and 15.9%, respectively. Reducing base doping levels to 1*10/sup 17/ cm/sup -3/ and decreasing the emitter thickness to 0.3-0.4 mu m for p-n cells led to improvements in radiation hardness as measured by EOL/BOL (end-of-life/beginning-of-life) efficiency ratios for irradiation of 10/sup 15/ cm/sup -2/ electrons at 1 MeV. Emitter thickness had a less dramatic effect on efficiencies and radiation resistance, with the optimum thickness appearing at about 0.28 mu m. These results are supported by modeling calculations.<
>