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Published January 2020 | public
Journal Article

Development of Lattice-Mismatched GaInAsP for Radiation Hardness


We develop lattice-mismatched GaInAsP as an alternative alloy to pure As-based alloys currently used in III–V multijunction solar cells. Increasing the alloy phosphorous and indium content while maintaining an optimal bandgap may allow high efficiency multijunction devices with increased radiation hardness. Here, 1.0-eV GaInAsP is developed and implemented into single and multijunction solar cell devices. The lattice-mismatched GaInAsP must be grown strain free, and the subcell thickness must be maintained below the thickness where surface-driven phase separation occurs. As observed in transmission electron microscopy and cathodoluminescence imaging, phase separation strengthens in the GaInAsP layer and leads to interfacial defect formation when the cell thickness is too great. We show single junction 1.0-eV Ga_(0.5)In_(0.5)As_(0.7)P_(0.3) with excellent carrier collection and a bandgap-voltage offset of 0.40 V. This material quality approaches that of 1.0-eV Ga_(0.7)In_(0.3)As used in inverted metamorphic multijunction devices, but has increased phosphorus content and consequently is expected to have a higher radiation resistance. We incorporate the 1.0-eV GaInAsP subcell into a 3-junction inverted metamorphic solar cell to test the performance of the subcell in a multijunction. No additional loss is observed upon integration into a multijunction cell: both the carrier collection and voltage of the GaInAsP subcell are unchanged from single junction devices. While further materials development and radiation testing is still required, these preliminary results indicate that lattice-mismatched GaInAsP can be effectively used in multijunction solar cells to replace radiation-soft materials.

Additional Information

© 2019 IEEE. Manuscript received June 10, 2019; revised August 26, 2019; accepted October 8, 2019. Date of publication October 31, 2019; date of current version December 23, 2019. This work was supported in part by Northrop Grumman under the Space Solar Power Initiative, in part by The Aerospace Corporation, in part by the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308 with Alliance for Sustainable Energy, LLC, the operator of the National Renewable Energy Laboratory, and California Institute of Technology under CRADA No. CRD-17-704, and in part by MRSEC Program of the NSF under Award No. DMR 1720256. The work of B. B. Haidet was supported by the National Science Foundation (NSF) Graduate Research Fellowship under Grant 1650114.

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October 18, 2023