Radiation resistant of upright metamorphic GaInP/GaInAs/Ge triple junction solar cells for space use

The electrical parameters and EQE spectral response of 1 MeV electron beam irradiated MOVPE grown lattice-matched (LM) and upright metamorphic (UMM) GaInP/GaInAs/Ge triple-junction solar cells have been investigated with different flux density and fluence range from
$5\times 10^{14}$
to
$1.5\times 10^{15}\mathbf{cm}^{-2}$
. The overall degradation of electrical parameters of UMM cell was higher than LM cell due to the existence of dislocation within the epitaxy active layers. It was observed that the EQE spectra degrade mainly in top and middle subcells, and top GaInP subcell in UMM cell showed better radiation resistance due to the higher InP composition. An artifact phenomenon was observed in bottom Ge subcell due to the low shunt resistance.