Performance of Ga/sub 0.47/In/sub 0.53/As cells over a range of proton energies

Abstract

Ga/sub 0.47/In/sub 0.53/As space power solar cells were processed by OMVPE and their characteristics determined at proton energies of 0.2, 0.5, and 3 MeV. Emphasis was on characteristics applicable to use of this cell as the low bandgap member of a monolithic, two terminal high efficiency InP/GaInAs cell. It was found that the radiation induced degradation in efficiency, I/sub sc/ V/sub oc/ and diffusion length increased with decreasing proton energy. When efficiency degradations were compared with InP it was observed that the present cells showed considerably more degradation over the entire energy range. Similar to InP, R/sub c/, the carrier removal rate, decreased with increasing proton energy. However, numerical values for R/sub c/ differed from those observed with InP. The difference is attributed to differing defect behavior between the two cell types. It was concluded that particular attention should be paid to the effects of low energy protons especially when the particle's track ends in one cell of the multibandgap device.