Flight degradation data of GaAs-on-Si solar cells mounted on highly irradiated ETS-VI [satellite]

Flight data of GaAs space solar cells fabricated on Si substrates (GaAs/Si) are analyzed by comparing with the data of GaAs cells on GaAs substrates (GaAs/GaAs). The initial performance of the GaAs/Si cells is comparable to the GaAs/GaAs cells. Both types of cells are mounted on the body of the ETS-VI satellite, which has been highly irradiated due to its anomalous orbit. The cells are estimated to be irradiated about ~10¹⁶ cm^-2 level of equivalent 1 MeV electrons at the end of the flight data collection. The independence of the radiation hardness of GaAs/Si cells with respect to the thickness of the cover glass has been shown from the flight data. Also, better performance of GaAs/Si cells compared to GaAs/GaAs cells has observed in the case when a thin (50 μm) cover glass is used and the cells are highly irradiated. The characteristics of the GaAs/Si cells, in addition to taking advantage of its light-weight substrate, are considered to be effective advantage for space missions