We have investigated wide-bandgap, metamorphic GaAs$_{1-x}$P$_x$ and In $_y$Ga $_{1-y}$P solar cells on GaAs as potential subcell materials for future 4–6 junction devices. We identified and characterized morphological defects in tensile GaAs $_{1-x}$P $_x$ graded buffers that lead to a local reduction in carrier collection and a global increase in threading dislocation density (TDD). Through adjustments to the graded buffer structure, we minimized the formation of morphological defects and, hence, obtained TDDs ≈ 10 $^6$ cm$^{-2}$ for films with lattice mismatch ≤1.2%. Metamorphic In $_y$Ga$_{1-y}$P solar cells were grown on these optimized GaAs$_{1-x}$P $_x$ graded buffers with bandgaps ($E_g$) as high as 2.07 eV and open-circuit voltages ($V_{oc}$) as large as 1.49 V. Such high bandgap materials will be necessary to serve as the top subcell in future 4–6 junction devices. We have also shown that the relaxed GaAs$_{1-x}$P $_x$ itself could act as an efficient lower subcell in a multijunction device. GaAs$_{0.66}$ P$_{0.34}$ single-junction solar cells with $E_g$ = 1.83 eV were fabricated with $V_{rm oc}$ = 1.28 V. Taken together, we have demonstrated that GaAs$_{1-x}$P $_x$ graded buffers are an appropriate platform for low-TDD, metamorphic GaAs$_{1-x}$P $_x$ and In $_y$Ga $_{1-y}$P solar cells, covering a wide bandgap range.

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PROJECT TITLE :Experimental Results From Performance Improvement and Radiation Hardening of Inverted Metamorphic Multijunction Solar CellsABSTRACT: This paper discusses results from continued development of inverted metamorphic
ABSTRACT:Metamorphic virus recognition is the most challenging task for antivirus software, because such viruses are the hardest to detect as they change their appearance and structure on each new infection. In this study, the

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