The observation of minority-carrier injection-enhanced annealing of radiation damage to InGa 0.5 P 0.5 /GaAs tandem solar cells is reported. Radiation resistance of InGaP/GaAs tandem solar cells as is similar with GaAs-on-Ge cells have been confirmed with 1 MeV electron irradiations. Moreover, minority-carrier injection under light illumination and forward bias conditions is shown to enhance defect annealing in InGaP and to result in the recovery of InGaP/GaAs tandem solar cell properties.

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... results suggest that the InGaP/GaAs͑/Ge͒ multijunction solar cells and InGaP-based devices have great potential for space applications. © 1997 American Institute of Physics. ͓S0003-6951͑97͒00912-1͔ Recently, InGa 0.5 P 0.5 /GaAs tandem solar cells have drawn increased attention because of the possibility of high conversion efficiency of over 30%. 1 These cells also have great potential for space applications, as demonstrated by the efficiency of over 30% attained for InGaP/GaAs 2-junction solar cells by the Japanese New Sunshine Project 2,3 and radiation hardness 4 of InGaP top cell materials. One of the key points for developing space solar cells is to improve their radiation resistance. We report here an observation of minority-carrier injection-enhanced annealing of radiation damage to metalorganic chemical vapor deposition ͑MOCVD͒-grown InGa 0.5 P 0.5 /GaAs tandem solar cells. The samples used in this study were n-on-p In 0.5 Ga 0.5 P/GaAs 2-junction solar cells, 5 grown on Zn-doped p-GaAs substrates by MOCVD with triethylgallium, trimethylindium, and phosphine as the source materials, and with silane and diethylzinc as n-and p-type dopants, with doublehetero structure InGaP top cells and GaAs bottom cells. The carrier concentrations of p-InGaP and p-GaAs base layer were 1-1.5ϫ10 17 cm Ϫ3 . The junction depths were 0.05-0.1 m. The best cell (2ϫ2 cm 2 ) with antireflective ͑AR͒ coating has demonstrated preirradiation efficiency with 26.9% (V oc ϭ2.451 V, I sc ϭ67.4 mA. FFϭ0.881), measured at NASDA, under AM0, 28°C. This value is a world record AM0 efficiency.