Radiation response of dual-junction Ga/sub y/In/sub 1-y/P/Ga/sub 1-x/In/sub x/As solar cells

Abstract
The radiation response of dual-junction Ga/sub y/In/sub 1-y/P/Ga/sub 1-x/In/sub x/As solar cells grown with 0.35<y<0.51 and 0.01<x<0.17 is presented. These lattice-mismatched structures were grown by metal-organic-vapor-phase-epitaxy on GaAs or Ge substrates. Measurement of the photovoltaic output of the cells made under simulated one-sun, AM0 spectral conditions shows that the new dual-junction Ga/sub x/In/sub 1-x/P/Ga/sub y/In/sub 1-y/As cells perform as well or better than commercially available multijunction cells. Measurement of the quantum efficiency gives insight into which subcell determines the total cell degradation under proton irradiation. As has been found previously for the Ga/sub y/In/sub 1-y/P/GaAs tandem cell, degradation of the new Ga/sub y/In/sub 1-y/P/Ga/sub 1-x/In/sub x/As material combination is controlled by the bottom solar cell. Analysis of the irradiation data is used to determine the basic mechanisms governing the radiation response of these devices, including the effect of stoichiometry, lattice-mismatch and cell structure.